Chapter 1 Boolean Logic and Gates

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Chapter 1

Boolean Logic and Gates


Circuit design is based on t he mat hemat ical branch of Boolean Logic, dealing wit h various
manipulat ions of t he values of TRUE and FALSE. You can see t hat t hese values can easily be
represent ed by 0's and 1's inside t he co
mput er. Boolean logic uses t he basic st at ement s AND,
OR, and NOT. Using t hese and a series of Boolean expressions, t he f inal out put would be one
TRUE or FALSE st at ement. Let me t ry t o illust rat e t his:


If A is true AND B is true, then (A AND B) is true

If

A is true AND B is false, then (A AND B) is false

If A is true OR B is false, then (A OR B) is true

If A is false OR B is false, then (A OR B) is false


If A is t rue and B is f alse, t hen some ot her condit ion t akes place. The let t er A and B can
represent
anyt hing needed in t he program. In programming languages, we use t he IF
st at ement t ypically t o show t hat IF some t hing is t rue, THEN do t his.


Since t ransist ors are eit her ON or OFF, represent ing 0 and 1, ands t hus could represent TRUE
or FALSE, placement

of t hese t ransist ors in various locat ions of a circuit will yield result s t hat
are based on Boolean logic. These designs are called Gat es. A gat e is an elect ronic device t hat
t akes in some input and out put s a single binary out put. Gat es are used t o do all

sort s of
t hings, but f or Boolean logic, we are concerned wit h t he AND, OR, and NOT gat es. These gat es
are designed t o out put Boolean result s.


An AND gat e would be t wo t ransist ors in a series circuit as shown in t he diagram t o t he right.
In order t o get
a value of 1 as an out put (t he binary equivalent t o TRUE) t hen bot h Input 1
and Input 2 would have t o be 1. That is, bot h condit ions must be t rue in order f or t hose
t ransist ors t o swit ch t o ON, complet e t he circuit, and creat e an Out put.


An OR gat e is si
milar. We have t wo t ransist ors wit h t wo input s. But, t he t ransist ors are locat ed
in parallel. So, if eit her one of t he t ransist ors close, t he circuit will produce an out put. This
corresponds t o t he Boolean logic of OR, where if eit her is t rue, t hen t he f in
al result is TRUE. A
diagram of t he OR gat e is below.


There is also a NOT gat e. It is const ruct ed a bit dif f erent ly, but t he principle is t he same. The
placement of t he t ransist ors, and in t
his case a resist or, f orms t he NOT Boolean expression.


A circuit is designed around t hese principles. Using various combinat ions of t hese gat es, you
can design gat es f or almost any purpose: loops, t est
-
f or
-
equalit y, mat hemat ical f unct ions, et c.
As you ca
n imagine, even designing one circuit t o simply add t wo numbers can t ake rat her
complex designs of various combinat ions of t hese basic gat es. A comput er chip is made up of
millions of such circuit s. Various opt imizat ions t o t he designs help t o increase ove
rall speed of
t he circuit s.


An int erest ing not e: 1
-
bit ADD circuit requires 3 NOT gat es, 16 AND gat es, and 6 OR gat es, f or
a t ot al of 25 gat es. To creat e a 32
-
bit ADD circuit would t hen t ake 800 gat es using a t ot al of
1,504 t ransist ors. In t he old vacuum

t ube based comput ers, t his many vacuum t ubes would
t ake up a space about t he size of a ref rigerat or. Today, t he complet e ADD circuit t akes up a
space smaller t han a pixel on t his screen, or t he period at t he end of t his sent ence.


The Binary Number System


A comput er runs on binary code. But, what is t his? basically, it is a number syst em. Let's look
at it:

Most people use a number syst em based on 10. We use t he digit s 0,1,2,3,4,5,6,7,8 and 9 t o
f orm our numbers. All numbers can be represent ed by any num
ber t imes 10 t o some power. For
inst ance:

14,393 = 1.4393 x 10^4

Using t hese numbers we can f orm int egers, decimals, et c. We all know t his, so let me not
delve int o t his any more.

Now, t he reason we cannot use t his syst em of numbering in t he comput er is

pret t y simple. it
would make lif e easier f or us. But, as we know, a comput er circuit is made out of t ransist ors.
Transist ors have t wo posit ions
-

on and of f. The comput er uses t hese posit ions t o represent 0
and 1. Since we do not have any syst ems wit h 10 s
t able posit ions, and we do have t he
t ransist or wit h 2 st able posit ions, we t hus use t he binary syst em.

The binary syst em uses base 2 inst ead of base 10 like we are used t o. To compare it, let's
again look at base 10:

234 = (2 x 10^2) + (3 x 10^1) + (4 x
10^0)

You can see how any number can be represent ed by a base of 10. In binary we use base 2:

10111 = (1 x 2^4) + (0 x 2^3) + (1 x 2^2) + (1 x 2^1) + (1 x 2^0)

10111 = 16 + 0 + 4 + 2 + 1 = 23

So, 10111 in binary is equal t o a value of 23. To represent i
nt egers, which can be posit ive or
negat ive, comput ers t ypically use a sign not at ion on t he binary. 0 is posit ive and 1 is negat ive
and t his number precedes t he t he rest of t he number. 1 10111 would be
-
23 f or example. How
does t he comput er dif f erent iat e t h
is f rom 110111? Simply be cont ext in t he program.

ASCII code is t he t erm f or t ext charact ers represent ed by t he comput er. Since comput ers ONLY
t hink in binary, ASCII charact ers are represent ed by cert ain binary numbers. Again, t he only
way t he comput er di
f f erent iat es bet ween t he ASCII charact er and t he number it self is by
cont ext. There is a whole chart showing all t he ASCII charact ers and t heir binary equivalent s,
but who t he hell needs t o see t hat?


Von Neumann Architecture



All comput ers share t he sam
e basic archit ect ure, whet her it be a mult i
-
million dollar mainf rame
or a Palm Pilot. All have memory, an I/O syst em, and arit hmet ic/logic unit, and a cont rol unit.
This t ype of archit ect ure is named Von Neumann archit ect ure af t er t he mat hemat ician who
con
ceived of t he design.


Memory


Comput er Memory is t hat subsyst em t hat serves as t emporary st orage f or all program
inst ruct ions and dat a t hat are being execut ed by t he comput er. It is t ypically called RAM.
Memory is divided up int o cells, each cell having
a unique address so t hat t he dat a can be
f et ched.


Input / Out put


This is t he subsyst em t hat allows t he comput er t o int eract wit h ot her devices and communicat e
t o t he out side world. It also is responsible f or program st orage, such as hard drive cont rol.


Arit hmet ic/Logic Unit


This is t hat subsyst em t hat perf orms all arit hmet ic operat ions and comparisons f or equalit y. In
t he Von Neumann design, t his and t he Cont rol Unit are separat e component s, but in modern
syst ems t hey are int egrat ed int o t he processor
. The ALU has 3 sect ions, t he regist er, t he ALU
circuit ry, and t he pat hways in bet ween. The regist er is basically a st orage cell t hat works like
RAM and holds t he result s of t he calculat ions. It is much f ast er t han RAM and is addresses
dif f erent ly. The ALU

circuit ry is t hat act ually perf orms t he calculat ions, and it is designed f rom
AND, OR, and NOT gat es just as any chip. The pat hways in bet ween are self
-
explanat ory
-

pat hways f or elect rical current wit hin t he ALU.


Cont rol Unit


The cont rol unit has t he
responsibilit y of (1) f et ching f rom memory t he next program
inst ruct ion t o be run, (2) decode it t o det ermine what needs t o be done, t hen (3) issue t he
proper command t o t he ALU, memory and I/O cont rollers t o get t he job done. These st eps are
done cont inuo
usly unt il t he last line of a program is done, which is usually QUIT or STOP.

At t he machine level, t he inst ruct ions execut ed by t he comput er are expressed in machine
language. Machine Language is in binary code and is organized by op code and address f ie
lds.
Op codes are special binary codes t hat t ell t he comput er what operat ions t o carry out. The
address f ields are locat ions in memory on which t hat part icular op code will act. All machine
language inst ruct ions are organized wit h t he op code f irst, t hen t
he memory addresses
f ollowing. For example: Let's assume we want t o add t wo number t oget her t hat are in memory
locat ions 99 and 100. Let's assume t he decimal 9 is t he op code f or t he ADD f unct ion. The
f ormat, t hen, f or t he command would be 9
-
99
-
100. Of cou
rse, t his is in decimal f orm and not
t he way t he comput er sees it. Convert t hese t o binary t o get:

0000100100000000011000110000000001100100

That's a 9, a 99, and a 100 put t oget her wit h no dashes. Now, you get an idea of just how a
comput er t hinks.

The
set of all operat ions a processor can do is called it s inst ruct ion set.




Function of each Major Computer Component


Each dif f erent part in a comput er has a dif f erent t ask t o perf orm. Each part works dif f erent ly
in order t o get it s job done. There are ma
ny misconcept ions about what part s do what job, and
here, we will set out t o correct t hem. Knowing what f unct ion each part has is very rewarding.
If one knows what part does one, t hey can easily narrow down problems in a comput er.


The Processor(CPU)

The
processor is known as t he brain of t he comput er. The processor is just a really f ast
calculat or. It adds, subt ract s, mult iplies and divides a mult it ude of numbers. There are t wo
part s of t he Processor t hat do t he mat h. The f irst part is called t he Int eger

unit. It's job is t o
t ake care of t he "easy" numbers, like
-
5, 13, 1/2, et c. It's mainly used in business
applicat ions, like word processors, spreadsheet s, and t he Windows Deskt op. The ot her half is
called t he Float ing Point Unit. It's job is t o t ake care

of t he really hard numbers, like t he
square root of 3, pi, "e.", and logarit hms. This part of t he CPU is mainly used in 3D games, t o
calculat e t he posit ion of pixels, and images.


The Hard Disk Drive(HDD)

The Hard Drive is simply a mult it ude of met al dis
ks t hat spin around inside your comput er,
wit h heads t hat move around t hose disks. Those heads read and writ e dat a t o t he met allic
disks. The reason f or using a Hard drive is because t he hard drive is t he only part inside a
comput er t hat st ores dat a while
t he comput er is of f. Your Hard Drive is what st ores all of your
set t ings, programs, and t he operat ing syst em while your comput er is of f. The only draw back
t o t he hard drive, is t hat it is mechanical. That means it has a t endency t o break down every
once i
n a while f or no reason, and it is slower t han elect ronic means of dat a st orage.


Random Access Memory(RAM)

The RAM is a chip t hat holds dat a, only as elect ricit y f lows t hough it. It is very f ast compared
t o t he Hard Drive, but is also expensive, which is

why we don't use it f or our primary dat a
st orage. RAM is used as an int erf ace bet ween t he Hard Drive and t he Processor. If t he
Processor needs some dat a t hat's on t he hard drive, t he RAM chipset will ret rieve t he dat a
f rom t he hard drive and put it int o
memory, so t he processor can access it f ast er. If t he
comput er runs out of room in t he RAM, it will make a f ile on your hard drive, called "Virt ual
RAM." "Virt ual RAM" is just an ext ension of real RAM on your Hard Drive. As said above, t he
Hard drive is mu
ch slower t han t he RAM, so when t he comput er get s t he dat a st raight f rom t he
Hard Drive, your comput er will also seem like it f reezes, because it will be running so slowly.
Once you shut your comput er of f, t here is not hing st ored in t he RAM, because t here
is no
elect ricit y f lowing t hough it.




Cache (L1 & L2)

The Cache is high speed RAM. It st ores commonly used dat a and inst ruct ions f rom t he
processor so t hat it doesn't have t o go t o t he slower RAM t o get it. This is why t he modern day
comput er is so f ast
. Wit hout cache, most processors would be limit ed in speed by t he RAM.
Wit hout it, your comput er would be running t erribly slow. The Cache is split up int o 2 dif f erent
Levels. The f irst level, L1, ranges in size f rom 32KB t o 128KB. It is split in half and
resides
wit h in t he CPU core, next t o t he Int eger and Float ing Point Unit. The f irst half st ores
commonly used dat a, and t he second half st ores common inst ruct ions t hat t he processor
carries out on t he dat a. The second level of cache, called L2, is f or dat
a only. Some L2 Caches
are on t he mot herboard. Ot hers are on a special cart ridge wit h t he CPU. Newer L2 Caches are
in t he CPU core, wit h t he L1 cache.


The Chipset

The chipset controls communication between the components. The chipset is split up into two

basic chips. The first chip, called the
North Bridge, handles communication between the AGP bus, (if it exists), RAM, processor, and the South Bridge of the chipset.

The
South Bridge handles all the Input and output of the computer, including the PCI and
ISA Bus. The Processor, Memory, Cache, and
Chipset all work together to function as a logical brain.

General PC St ruct ure


Inside a comput er case must be jam
-
packed wit h wires. Act ually, a t ypical PC has a lot of
wast ed space inside t he case. It is also, a
s I said, a collect ion of part s. If a part breaks, you
just buy a new one and t hrow it in. A PC does not have many part s at all and it's f airly
st raight
-
f orward.


A case is a rect angular box which houses all t he PC innards. Taking t he cover of f t he case
r
eveals t he gut s. up in t he corner is a gray box wit h a bunch of wires coming out. That is t he
power supply, Swit ch Mode Power Supply (SMPS). That device t akes t he power f rom t he
elect rical out let in t he wall and dist ribut es it t o t he devices wit hin t he com
put er. At t he ends
of each wire bunch will be a whit e plug. This plug plugs int o each device wit hin t he PC.


The largest circuit board in t he PC is t he mot herboard. The mot herboard usually lies f lat or
st ands upright against t he side of t he case. All t he
part s in t he PC is connect ed t o t he
mot herboard. The mot herboard serves as t he communicat ion cent er of t he PC. All dat a moves
t hrough it. All of t hose lit t le elect rical et chings in t he board it self are t he lit t le roadways t hat
t he dat a and elect ricit y move

around on.


In a big slot on t he mot herboard is t he main processor, or CPU. The CPU will have a big f an
hanging of f it. This serves t o keep t he processor cool. Wit hout t he f an, it would boil it self. The
processor is t he "brain" of t he PC. Usually below t
he processor are a series of smaller circuit
boards, mount ed perpendicular t o t he mot herboard and each in it's own slot. Each of t hese
boards are your expansion cards. They are your modem, sound card, video card, net working
card, and any ot her various card
s you may have. Each card is modular and separat e, meaning
you can remove t he cards and replace t hem wit h ease.


You will also see the various storage devices of the computer. All but the hard drive will be mounted so as to stick out the
front of the
case

when the case cover is on. All drives have a power cord and a wide, gray cable going into it. These wide, gray cables are cal
led
IDE cables. "IDE" refers to the type of data transfer used on the PC. Data travels over these cables and this is how data mov
e
s from
the drives back to the processor in order to be manipulated.


Chapter 2

Processors


A CPU History


CPUs have gone t hrough many changes t hrough t he f ew years since Int el came out wit h t he
f irst one. IBM chose Int el's 8088 processor f or t he brains of

t he f irst PC. This choice by IBM
made Int el t he leader of t he CPU market. They usually come out wit h t he new ideas f irst. Then
companies such as AMD and Cyrix come in wit h t heir versions, usually wit h some minor
improvement s and slight ly f ast er.

Int el pr
ocessors have gone t hrough f ive generat ions. A sixt h is t aking hold. The f irst f our
generat ions t ook on t he "8" as t he series name, which is why t he t echnical t ypes ref er t o t his
f amily of chips as t he 8088, 8086, and 80186. This goes right on up t o t he 80
486, or just 486.
Then came along t he Pent ium. Int el went of f and changed t he name on t his one. Anyway, t he
higher t he chip number, t he more powerf ul t he chip is, and t he more cost ly.


The f ollowing chips are t he Leaders of t he comput er world.




Int el 808
6 (1978)

This chip was skipped over for the original PC, but was used in a few later computers that didn't
amount to much. It was a true 16
-
bit processor and talked with its cards via a 16 wire data connection.




Int el 8088 (1979)

This is the chip used in
the first PC. It was 16
-
bit, but it talked to the cards via a 8
-
bit connection. It ran
at a whopping 4 MHz and could address only 1 MB of RAM.




NEC V20 and V30 (1981)

Clones of t he 8088 and 8086. They are supposed t o be about 30% f ast er t han t he Int el
one
s.




Int el 80186


The 186 was a popular chip. Many versions have been developed in it s hist ory. Buyers
could choose f rom CHMOS or HMOS, 8
-
bit or 16
-
bit versions, depending on what t hey
needed. A CHMOS chip could run at t wice t he clock speed and at one f ourt
h t he power
of t he HMOS chip. In 1990, Int el came out wit h t he Enhanced 186 f amily. They all
shared a common core design. t hey had a 1
-
micron

core design and ran at about
25MHz at 3 volt s.




Int el 80
286 (1982)

A 16
-
bit processor capable of addressing up t o 16 MB of RAM. This chip is able t o work
wit h
virt ual memory
. The 286 was t he f irst "real" processor. It int roduced t he concept
of prot ect
ed mode. It has t he abilit y t o mult it ask, having dif f erent programs run
separat ely but at t he same t ime. This abilit y was not t aken advant age of by DOS, but
f ut ure
Operat ing Syst ems
, such as Windows, cou
ld play wit h t his new f eat ure. This
chip was used by IBM in it s Advanced Technology PC AT. It ran at 6 MHz, but lat er
edit ions of t he chip ran as high as 20 MHz.




Int el 386 (1988)


Wit h t his chip, PCs began t o be more usef ul. The 386 was t he f irst 32
-
bit p
rocessor f or
PCs. It could, as a result, crunch t wice as much dat a on each clock cycle and it could
play around wit h 32
-
bit cards. It can t alk t o as much as 4 GB of real memory and 64
TB of virt ual memory. This Processor could also t eam up wit h a
mat h coprocessor
,
called t he 80387. It could also use processor cache, all 16 byt es of it. The reduced
version of t his chip is t he 386SX. This is a low
-
f at chip, cheaper t o make. It t alked
wit h t he c
ards via a 16
-
bit pat h. 386s range in speed f rom 12.5MHz t o 33MHz. 386
chips were designed t o be user f riendly. All chips in t he f amily were pin
-
f or
-
pin
compat ible and t hey were binary compat ible wit h t he previous 186 chips, meaning t hat
users didn't have

t o get new sof t ware t o use it. Also, t he 386 of f ered power f riendly
f eat ures such as low volt age requirement s and Syst em Management Mode (SMM) which
could power down various component s t o save power. Overall, t his chip was a big st ep
f or chip development.

It set t he st andard t hat many lat er chips would f ollow. It of f ered
a simple design which developers could easily design f or.




Int el 486 (1991)

The 486 brought t he brains of a 386 t oget her wit h an int ernal mat h coprocessor. It
was much f ast er. This chip h
as been pushed t o 120 MHz and is st ill in use t oday, in
older syst ems.

The f irst member of t he 486 f amily was t he 486SX. It was very power, ef f icient and
perf ormed well f or t he t ime. The ef f icient design led t o new packaging innovat ions.
The 486SX came in

a 176 lead Thin Quad Flat Pack (TQFP) package and was about t he
t hickness of a quart er.

The next members of t he 486 f amily were t he DX2s and DX4s. Their speeds were
obt ained due t o t he speed
-
mult iplying t echnology which enabled t he chip t o operat e at
clo
ck cycles great er t han t hat of t he bus. They also int roduced t he concept of
RISC
.
Reduced inst ruct ion set chips (RISC) do just a f ew t hings, but really f ast. This made
t his chip more ef f icient and set
it apart f rom t he older x86 chips. The DX2 of f ered 8 KB
of writ e
-
t hrough cache and t he DX4 of f ered 16 KB. This cache helps t he chip maint ain
it s one clock cycle per inst ruct ion given t hrough t he use of RISC.

It was split int o SX and DX versions. Bot h were

complet ely 32
-
bit, but t he SX lacks t he
mat h coprocessor. Nevert heless, t he SX version is roughly t wice as f ast as t he 386.
Act ually, t he mat h coprocessor in t he SX is t here, just disabled f or f inancial purposes.




The Pent ium (1993)

Int el brought t he PC t
o t he 64
-
bit level wit h t he Pent ium Processor in 1993. It has 3.3
million t ransist ors and perf orms at 100 million inst ruct ions per second (MIPS).

The Pent ium f amily includes t he 75/90/100/120/133/150/166/200/233 clock speeds. It
is compat ible wit h all of
t he older OS's including DOS, Windows 3.1, Unix, and OS/2.
It s superscalar design can execut e t wo inst ruct ions per clock cycle. The separat e
caches and t he pipelined f loat ing point unit increase it s perf ormance beyond t he x86
chips. It has SL power managem
ent f eat ures and has t he abilit y t o work as a t eam wit h
anot her Pent ium. The chip t alks over a 64
-
bit bus t o it s cards. It has 273 pins t hat
connect it t o t he mot herboard. Int ernally, t hough, it is really t wo 32
-
bit chips chained
t oget her t hat split t he wo
rk. The chip comes wit h 16 K of built in cache.

This chip, although fast, gets really hot. So, the use of a CPU fan is required with them. Intel has released more efficient
versions
of the chip that operate at 3.3 volts, rather than the usual 5 volts. Thi
s has reduced the heat some.

The processor has a burst mode t hat loads 256
-
bit chunks of dat a int o t he dat a cache
in a single clock cycle. It can t ransf er dat a t o t he memory at up t o 528 MB/Sec. Also,
Int el t ook it upon t hemselves t o hardwire several, hea
vily used commands int o t he
chip. This bypasses t he t ypical microcode library of commands. It also has a built in
self t est t hat t est s it self upon reset t ing.




The Pent ium Pro


This is a RISC chip with a 486 hardware emulator on it, running at 200 MHz or b
elow. Several
techniques are used by this chip to produce more performance than its predecessors; speed is achieved
by dividing processing into more stages, and more work is done within each clock cycle; three
instructions can be decoded in each one, as op
posed to two for the Pentium.

In additions, instruction decoding and execution are decoupled, which means that instructions can still
be executed if one pipeline stops (such as when one instruction is waiting for data from memory; the
Pentium would stop a
ll processing at this point). Instructions are sometimes executed out of order, that
is, not necessarily as written down in the program, but rather when information is available, although
they won't be much out of sequence; just enough to make things run s
moother.

It has a 8K cache
f or programs and dat a, but it will be a t wo chip set, wit h t he processor and a 256K
L2 cache

in t he same package. It is opt imized f or 32
-
bit code, so will run 16
-
bit cod
e no f ast er t han
a Pent ium, which is a big drag down. It ’s st ill a great processor f or servers, being it can
be in mult iprocessor syst ems wit h 4 processors, unlike t he newer Pent ium II (see below),
which can only be in dual CPU syst ems. Anot her good t hing
about t he Pent ium Pro is t hat
wit h t he use of a Pent ium 2 overdrive processor, you have all t he perks of a normal
Pent ium II, but t he L2 cache is f ull speed, and you get t he mult iprocessor support of t he
original Pent ium Pro.




The Pent ium II


The Pentium
II is kind of like the child of a Pentium MMX mother and the Pentium Pro Father. But
like real life, it doesn’t combine the best of it’s parents. It has an onboard L2 cache, but it runs at ½
speed, not at full speed. It can be used in Multiprocessor enviro
nments, but only in dual CPU areas.
Instead of the usual square package design, it comes in a Single Edge Contact (S.E.C.) cartridge. This
design offers higher performance through higher bus speeds. The core and the L2 cache are enclosed in
a plastic and m
etal cartridge, and this connects to the motherboard via a single edge connector instead
of a bunch of little pins typical of previous processors.




The Celeron

During t he t ime of t he Pent ium II wit h t he 100MHz Front side Bus, Int el f ound t hat it
could spli
t it's current market and sell lower cost and lower perf ormance chips and st ill
make a prof it. Wit h t his in mind, Int el creat ed t he f irst "Value" processor, named t he
Celeron. It was basically a Pent ium II, but didn't have t he half speed cache, in f act,
t h
e f irst Celeron's had no cache at all. This was f ound t o be a horrible mist ake, and
short ly Int el decided t o add 128KB of onchip L2 cache. Because t he cache was no
longer a limit ing f act or in overclocking, t hese 66MHz f ront side bus chips easily made it
up
t o t he 100MHz bus, a 50% overclock. Many hardcore t echs rushed out t o purchase
one of t hese chips, and overclock t hem madly because t he price / perf ormance rat io
was out st anding. Sooner or lat er, Int el dit ched t he PCB t he Celeron was on and creat ed
a

socke
t ed Celeron, similar t o it's Pent ium MMX socket ed chips.




The Pent ium
iii


This is basically a Pentium II, but with a newer MMX, which has 70 new instructions that increased the 3D performance,
and it run faster. It also had an electronic chip ID, which w
as supposed to be good, but the underworld of the Internet is
rebelling because that doesn’t allow for overclocking anymore. The reason they do that is to save money. They don’t have
to change the core design, which will cost money, to make a slower chip t
han they have technology for.

Around t he t ime of 600Mhz Pent ium iii, Int el t ook t he 512KB of half speed cache, and
made 256KB of f ull speed onchip cache wit h it. Just as wit h t he f irst Celeron, Int el
f ound t hat t he PCB was unnecessary, and moved t he chip i
nt o t he Socket 370 f ormat.
While doing t his, it also shrunk t he chip down t o t he 0.18micron process, as well as
adding SSE2 and a f ew t weaks t o t he L2 Cache st ruct ure.




Celeron II

Just as t he Pent ium iii was a Pent ium II wit h SSE and a f ew added f eat ures,
t he
Celeron II is simply a Celeron wit h a SSE, SSE2, and a f ew added f eat ures. In f act, t he
Celeron II is just like a Socket 370 Pent ium iii, but wit h half t he L2 cache t hat runs at
a slight ly slower speed. To be very t echnical, t he Celeron II is a Pent ium

iii. Int el
simply programs t he chip t o disable half of t he cache and make it slower, in order f or
t hem t o sell it in t he "Value" market and st ill make a prof it in t hat sect or.


Cooling



Back in t he 386 days, t here wasn't a need f or a special cooling sys
t em because t he chip was
slow and did not have many t ransist ors, t heref ore t he air f low f rom t he power supply was
enough t o cool t he chip. Today t hough, cooling is a very import ant issue. There are several
ways t o cool t he processor. Wit h t he release of t h
e 486, cooling became an issue. Wit h t he
slower 486's, it wasn't really a big deal, but wit h t he 486DX
-
66, cooling was an issue. This
clock
-
doubled chip got pret t y hot. From t hen on, chips ran f ast er and hot t er. All chips used
t oday require a special cooli
ng syst em. How much cooling depends on t he processor, t he case,
and t he t ype of cooling syst em you are using.

The t ype of processor is t he biggest variable in t he amount and t ype of cooling needed. For
example, t he Cyrix 6x86 is a nice Pent ium alt ernat ive
, but runs much hot t er t han t he Pent ium.
Run
-
of
-
t he
-
mill f ans could not keep it cool enough, so Cyrix had t o design a special heat sink
and f an t o keep t he chip cool.


Cooling Problems


A processor that is not cooled enough will show some strange errors.
Every processor has a safe range of temperatures that it can
handle. Once the temperature gets above that point, one will usually see random error messages. Many times, one will not susp
ect that
cooling is the problem because the error will seem to be comi
ng from another part. Common errors are system crashes, lockups, and
surprise reboots. It can also have program errors and memory errors along with many other things. Most cooling hardware is de
signed
for the AT case. The AT design is very poor when proces
sor cooling is concerned. An independent cooling system is required. In the
AT design, the processor is far away from the power supply. Also the fan blows out of the system instead of in, so there is n
ot much of
an air flow inside the case.

With the ATX d
esign, the processor was placed near a power supply that blows air directly over the chip. This helps quite a bit in
cooling, placing extra air flow over the processor. A CPU fan, though, is still recommended. With ATX, the air flow is more
conducive to co
oling. A case fan in the front pulls air in through the bezel. As heat rises, the power supply blows the air out the top,
rear of the case. If your case supports it, I would also recommend a case fan in the rear toward the top. Being that heat ris
es, you w
ant
the maximum air being blown out from the top of the case.

Heat Sinks


Heat sinks are used in many electronic devices for cooling, but for our purposes here, they are placed on processors to cool
them. The
operation is simple. It is a piece of metal, u
sually aluminum, with large fins protruding upward. This is placed on the chip. The fins, in
effect, increase the surface area of the chip's top, therefore allowing the heat to spread to more area. This reduces the hea
t. Then the air
flow from the fan cool
s the heat sink down. The larger and more pronounced the fins, the better the cooling will be. Some super fast
processors have truly huge heat sinks. We are also now seeing heat sinks on the video processors of our best video cards.

There are two types of

heat sinks. One is the passive heat sink. This type just sits there and has no moving parts. The other type, most
often used on processors, is the active heat sink. It is called active because it has a moving part, the fan. The heat sink i
s attached to
th
e processor in two ways. Some chips are shipped with heat sinks already glued on. Others are alone, and the heat sink must be

clipped on. In this case, a special chemical called heat sink compound is sometimes placed between the two for better heat tr
ansfe
r.
This is a white paste that is spread onto the processor. Very little is needed, just enough to fill in the gap of air that wo
uld be there
without the compound.

Guide to Slots, Sockets and Slockets


Here is a quick rundown of all the different sockets an
d slots for processors:


Socket 1

This is an old slot. It s f ound on 486 mot herboards and support s 486 chips, plus t he DX2, DX4
Overdrive. It cont ains 169 pins and operat es at 5 volt s. The only overdrive it will support is
t he DX4 Overdrive.


Socket 2

Thi
s Int el socket is a minor upgrade f rom t he Socket 1. It has 238 pins and is st ill 5 volt.
Alt hough it is st ill a 486 socket and support s all t he chips Socket 1 does, it has t he minor
addit ion of being able t o support a Pent ium OverDrive.


Socket 3

Anot her

Int el socket, cont aining 237 pins. It operat es at 5 volt s, but has t he added capabilit y
of operat ing at 3.3 volt s, swit chable wit h a jumper set t ing on t he mot herboard. It support s all
of t he Socket 2 processor wit h t he addit ion of t he 5x86. It is consider
ed t he lat est of t he 486
socket s.



Socket 4

We move int o Pent ium class machines wit h t he Socket 4, by Int el. This socket has 273 pins. It
operat es at a whopping 5 volt s. Due t o t his volt age, t his socket basically had no where t o go
but t he hist ory books.
It only support s t he low
-
end Pent ium 60
-
66 and t he Overdrive because
t hese chips are t he only Pent iums operat ing at 5 volt s. Beginning wit h t he Pent ium
-
75, Int el
moved t o t he 3.3 volt chip.


Socket 5

This socket operat es at 3.3 volt s wit h 320 pins. It sup
port s Pent ium class chips f rom 75MHz t o
133MHz. Newer chips will not f it because t hey need an ext ra pin. Socket 5 has been replaced
by t he more advanced Socket 7.


Socket 6

It is meant f or 486's. It is only a slight ly more advanced Socket 3 wit h 235 pins
and 3.3 volt
operat ion. This socket is f orgot t en. The market never moved t o use it because it came out
when 486's were already going of out st yle and manuf act urers couldn't see pumping money
int o changing t heir designs f or a 486.


Socket 7

Socket 7 is t he

most popular and widely used socket. It cont ains 321 pins and operat es in t he
2.5
-
3.3 volt range. It support s all Pent ium class chips, f rom 75MHz on up, MMX processors, t he
K5, K6, K6
-
2, K6
-
3, 6x86, M2 and M3, and Pent ium MMX Overdrives. This socket is t h
e indust ry
st andard and is being used f or sixt h
-
generat ion chips by IDT, AMD and Cyrix. Int el, however,
decided t o abandon t he socket f or it's sixt h
-
generat ion lineup. Socket 7 boards incorporat e t he
volt age regulat or which makes volt ages lower t han t he na
t ive 3.3 volt possible.




Socket 8

This is a high
-
end socket used primarily f or t he Pent ium Pro. It has 387 pins and operat es at
3.1/3.3 volt s. This socket only handles t he Pent ium Pro. It is designed especially t o handle t he
dual
-
cavit y st ruct ure of t he

chip. Since Int el decided t o move on t o Slot 1, t he Socket 8 is a
sort of dead end.


Slot 1

Int el complet ely changed t he scene wit h t his slot. It, inst ead of accept ing t he usual square
chip wit h pins on t he bot t om, t akes t he processor on a daught ercard. T
he daught ercard allows
f ast communicat ion bet ween t he processor and t he L2 cache, which lies on t he card it self. The
slot it self has 242 pins and operat es at 2.8
-
3.3 volt s. The Slot 1 is used mainly f or t he P2,P3
and Celeron, but Pent ium Pro users can use
t he slot by mount ing t heir processors in a socket 8
on a daught ercard which is t hen insert ed int o t he Slot 1. This gave Pent ium Pro users t he
abilit y t o upgrade.


Slot 2

A chip packaging design used in Int el Pent ium II chipset s, st art ing wit h t he Xeon CPU.

While
t he Slot 1 int erf ace f eat ures a 242
-
cont act connect or, Slot 2 uses a somewhat wider 330
-
cont act connect or. The biggest dif f erence bet ween Slot 1 and Slot 2, t hough, is t hat t he Slot 2
design allows t he CPU t o communicat e wit h t he L2 cache at t he CPU
's f ull clock speed. In
cont rast, Slot 1 only support s communicat ion bet ween t he L2 cache and CPU at half t he CPU's
clock speed.


Socket 370

Socket 370 is named f or t he number of pins t his cert ain socket has. Af t er Int el f ound a way t o
cheaply put t he cac
he of a CPU on t he die, it f ound t hat a separat e PCB f or t he processor was
cost ly and useless. Int el t hen t ook t he Chip of f of t he PCB, and creat ed Socket 370. It's
basically Socket 7 wit h an ext ra row of pins on all f our sides. The f irst processors t o use

it
were t he PPGA Celeron, t hen quickly f ollowing were t he FC
-
PGA Pent ium iii processors along
wit h t he Celeron II line. Socket 370 chips can be placed on a daughercard just like Socket 8
chips in order t o f it int o a Slot 1 Int erf ace. Socket 370 is also ma
de t o use previous Socket 7
heat sinks, alt hough most of t hem are t oo small t o cool t hese modern processors. This Socket is
used f or Pent ium iii, Celeron, and Celeron II processors.


Slot A

This is a new propriet ary slot design AMD decided t o use wit h t he
At hlon processor. Design
wise, it is similar t o t he Slot 1. But, Slot A uses a dif f erent prot ocol, called EV6. Using t his bus
prot ocol, which was creat ed by Digit al, AMD can increase t he RAM t o CPU dat a t ransf er t o
200MHz, giving us a 200MHz f ront side bus.

AMD had t o use t heir own Slot design since Int el
had ef f ect ively pat ent ed t he Slot 1 design so t hat AMD could not use it. Now, wit h t he At hlon
becoming more popular, more and more Slot A boards are coming out so t hat syst ems based on
t he At hlon are becomi
ng more common.


Socket A

Just as Int el f ound it's cheaper t o leave t he PCB of f of it's processors, AMD did t he same. It's
At hlon and Duron processors using t he .18 micron process bot h use Socket A. It support s t he
200MHz EV6 bus, as well as t he new 266MHz

EV6 bus. Unlike Socket 370, it requires a slight
modif icat ion a Socket 7 heat sink in order t o be used properly. Also, unlike Socket 370, t here is
no daughercard t hat provides Socket A chips t o be plugged int o Slot A int erf aces. Socket A also
of f ers many m
ore pins t han Socket 370, 462 in t ot al. Socket 370 chips can not plug int o Socket
A, and vise versa. This Socket is used f or bot h At hlon and Duron Processors.


Slockets

The slocket is a weird lit t le cont rapt ion. It s basically Slot 1 t o Socket 370 adapt er.

It comes in
ot her f lavors t oo. By doing a bunch of elect rical work
-
arounds, it is able t o successf ully
rerout e t he current s and make t he dif f erent int erf aces adapt. Some of t hem even have cut e
lit t le elect rical t ricks t hat allow t hings such as dual
-
proces
sor or overclocking despit e t he
clock
-
locking.


Overclocking Your Processor


Overclocking is going mainst ream, it seems, among end users. Almost all hardware web sit es
discuss t he subject, and most make it seem like it's easy, and t hat everyone does it. O
f
course, manuf act urers don't want you t o do it t o t heir processors. Some even clock
-
lock t heir
processors. But, on t he int ernet, it runs rampant. In many cases, t hough, you don't get t he
real st ory behind it. Of course, it can speed up t he syst em some, bu
t it has t he pot ent ial t o do
damage t o t he syst em.

So, yes, overclocking is a viable opt ion, if you know what you're doing, and you t hink t he
processor can handle it, but it should not be done by most people. It should not be done
especially on syst ems t h
at are very import ant in your daily operat ion. If you use your comput er
f or work or have import ant dat a on it, do not overclock.


Processor Voltage


In t oday's processors, volt age is a major concern. In t he pre
-
486DX66 days, everyt hing was 5
volt, so t here

was no quest ion on volt age, and nobody cared. Today, volt age concerns plague
every CPU buyer.




The more power t he CPU t akes, t he more heat it creat es. Heat is not good on t he
processor and can be a barrier in creat ing f ast processors. So, lowering t he vo
lt age in
f ast chips reduces t he heat.



Since lapt ops run on bat t eries, t he amount of power consumed by t he processor is a
large f act or. The lower t he volt age, t hen, t he longer t he bat t ery will last.



Many t imes, large companies are running hundreds of PC's

at one t ime, t heref ore t he
amount of power used is a concern.



Dual Volt age


Older CPU's t ypically ran at one volt age, 5 volt s. There was not hing else. As chips got f ast er
and power became a concern, designers dropped t he chip volt age down t o 3.3 volt s.

Then, as
chips got even f ast er and more powerf ul, t here was a need t o go below 3.3 volt s. So,
designers began t o incorporat e a split volt age design, or dual volt age. In t hese chips, t he
ext ernal I/O volt age is 3.3 volt s so t hat it is compat ible wit h ot her

mot herboards and t heir
component s. The core volt age, t hen, is lower, maybe 2.9 or 2.5 volt s. So, t he chip operat es at
2.5 volt s while it t alks t o t he mot herboard at 3.3 volt s. This keeps mot herboard designs t he
same. The only component s t hat changes is t h
e volt age regulat or t hat supplies t he correct
volt age t o t he CPU socket.

The core volt age is always changing wit h new processor designs. The new chips, f or t he most
part, use core volt ages below 3 volt. The Int el Pent iumMMX, Cyrix 6x86, and t he K6 use cor
e
volt ages of 2.8 or 2.9 volt s. The K6
-
233 is t he silly chip t hat operat es at a 3.2 volt core, way
beyond t he usual. The volt age regulat or convert s t he power t o t he correct core volt age f or t he
processor in t he socket. This is a reason f or t he list of proc
essors a mot herboard support s. The
volt age regulat or is designed t o supply only cert ain volt ages.


Volt ages of Specific Processors


Here is a table with the voltages of all common CPU's:




Processor

External Voltage

Core
Voltage

8088

5

5

8086

5

5

80286

5

5

80386S X (DX)

5

5

80486DX (S X)

5

5

I nt el 486DX2

5

5

A MD, C y ri x 486DX2

3.3

3.3

486DX4 (A l l mak es)

3.3

3.3

5x86 (A MD, C y ri x)

3.45

3.45

P ent i um 60, 66

5

5

P ent i um 75
-
200

3.3/3.52

3.3/3.52

P ent i um MMX

3.3

2.8

6x86

3.3

3.3

6x86L

3.3

2.8

A MD K5

3.52

3.52

P ent i um P ro
-
150

3.1

3.1

P ent i um P ro
-
166+

3.3

3.3

P ent i um I I (Kl amat h)

3.3

2.8

P ent i um I I Deschut es/ C el eron Mendoci no


3.3

2.0

P ent i um i i i (Kat mai )

3.3

2.0

P ent i um i i i (C oppermi ne)

3.3

1.65
-
1.75*

C el eron I I (C oppermi ne 128)

3.3

1.5
-
1.65*

A MD A t hl on (
S ock et A )

3.3

1.6
-
1.8*

A MD A t hl on (S l ot A )

3.3

1.6
-
1.8*

A MD Duron (S ock et A )

3.3

1.6

A MD K6
-
2+ / K6
-
I I I +

3.3

1.8
-
2.0*

A MD K6
-
I I I

3.3

2.2

A MD K6
-
2 w/ 3DN ow!

3.3

2.2

A MD K6 266/ 300

3.3

2.2

A MD K6
-
(166,200)

3.3

2.9

A MD K6
-
233

3.3

3.2

6x86L

3.3

2.8

6x86MX


3.
3

2.9

An Ast erisk (*) denot es t hat t he volt age of t he processor depends on t he int ernal reversion
and t he clock speed of t he chip. Please check t he chip it self in order t o f ind t he correct
volt age t o run it at.


Chapter 3

Motherboards


The motherboard is

the most important part of your computer. It is also one of the most compared, critiqued, and reviewed pieces of
hardware. Often, on the internet, you'll find reviews and debates over which board is best or which chipset is best. Sometime
s the
average rea
der gets left in the dust. We will try to explain what's going on and what it all means.


Chipsets


The mot herboard is generally t hought t o be t he most import ant part of a comput er. And yes, it
is. However, t he chipset on t he mot herboard is t he most impor
t ant part of t he board it self as it
def ines almost everyt hing about t he syst em. We have said t hat t he CPU is t he brain, t he BIOS
is t he nervous syst em. Well, t he chipset is like t he heart.

The chipset cont rols t he syst em and it s capabilit ies. It is t he hu
b of all dat a t ransf er. It is a
series of chips on t he mot herboard, easily ident if ied as t he largest chips on t he board wit h t he
except ion of t he CPU. Chip set s are int egrat ed, meaning t hey are soldered ont o t he board and
are not upgradable wit hout buying
a whole new mot herboard.

All dat a must go t hrough t he chipset. All component s t alk t o t he CPU t hrough t he chipset. To
make order out of all t his dat a, t he chipset makes use of t he DMA cont roller and t he bus
cont roller.

Since chipset s are so import ant and

have t o know how t o communicat e wit h all component s,
t hey must be designed f or your conf igurat ion and CPU. The chipset maker needs t o keep up
wit h BIOS and memory makers, since all of t hese part s work t oget her and t he chipset is t he
hub of it all.


A chi
pset is designed by t he manuf act urer t o work wit h a specif ic set of processors. Most
chipset s only support one generat ion of processors: most chipset s are geared specif ically f or
486 t ype syst ems, Pent ium class syst ems, or Pent ium Pro / Pent ium II syst ems.

Why make it
complicat ed like t hat? Well, t he reason is simple. The design of t he cont rol circuit ry must be
dif f erent f or each processor generat ion due t o t he dif f erent ways t hey employ cache, access
memory, et c. For example, t he Pent ium Pro and Pent ium II

have level 2 cache wit hin t he CPU
it self, so obviously t hey would need a dif f erent circuit ry design t han t he Pent ium, which has
level 2 cache on t he mot herboard.

Most mot herboards t hat support Int el Pent ium processors also support t heir equivalent s f rom
AMD and Cyrix. In f act, usually, t hese chips inst all just as an Int el chip, ot her t han t he f act
t hat you may need t o set dif f erent jumper set t ings f or bus speed or volt ages. I must not e
here, t hough, t hat t he dif f erent volt ages of t he CPU's and whet her t he

board will support it is
not a f unct ion of t he chipset, but of t he volt age regulat or. But, since Int el is t he largest
manuf act urer of Pent ium
-
class and higher chipset s, AMD and Cyrix are at a disadvant age. AMD
has evened out t he f ield a t ad wit h t heir AMD
-
640 chipset, aimed at opt imizing t he
perf ormance of AMD's K6. But also, companies such as Via and ALI are producing Super 7
chipset s aimed at non
-
Int el processors.


Processor Speed Support


Fast er processors require chipset s capable of handling t hem. The

specif icat ion of t he processor
speed is done using t wo paramet ers: t he memory bus speed and t he processor mult iplier. The
memory bus speed is t he processor's "ext ernal" speed, t he speed it t alks t o t he rest of t he
comput er at. The memory bus speed also (n
ormally) dict at es t he speed of t he PCI local bus,
which in most mot herboards runs at half t he memory bus speed. Typical modern bus speeds
are 50, 60, 66 and 75 MHz. Fast er syst ems use 83MHz or even 100MHz bus speeds. The
mult iplier represent s t he number by

which t he memory bus speed must be mult iplied t o obt ain
t he processor speed. Mult ipliers on modern PCs are normally 1.5x, 2x, 2.5x, 3x, 3.5x, or 4x,
t hough f ast er processors will event ually increase t his.

The chipset runs at t he speed of t he mot herboard
bus, usually 66MHz in most syst ems. Wit h
chipset s such as Int el's 440BX, Via's MVP3, and ALI's Aladdin V, many newer PC's are pushing
100MHz bus speeds. This part icularly helps t he perf ormance of Super 7 syst ems because t he L2
cache runs at t he speed of t h
e mot herboard. This doubles L2 cache speeds. Wit h Pent ium II's,
t he L2 cache is already running at 1/2 t he speed of t he processor, so increasing t he bus t o
100MHz won't help out as much.

The range of t he processor speeds support ed by t he chipset is indica
t ed, generally, by looking
at t he range of support ed memory bus speeds and mult ipliers. A t ypical Pent ium chipset will
support bus speeds of 50 t o 66 MHz wit h a mult iplier range of 1.5x t o 3.0x. This yields speeds
of 75, 90, 100, 120, 133, 150, 166 and 200

MHz.


Mult iple Processor Support


Some chipset s support t he abilit y t o make mot herboards t hat support t wo or f our processors.
The chipset circuit ry coordinat es t he act ivit ies of t he processors so t hat t hey don't int erf ere
wit h each ot her, and works wit h
t he operat ing syst em sof t ware t o share t he load bet ween
t hem. The st andard f or mult iprocessing in Pent ium and Pent ium Pro PCs is Int el's SMP
(symmet ric mult iprocessing). It only works wit h Int el processors. Of course, I should make
not e t hat, in order t o s
uccessf ully have a mult i
-
processor syst em, t hat much more t han a
support ing chipset is needed. You must have compat ible CPU's and a support ing OS.


Most modern comput ers use t hree bus t ypes: t he ISA bus f or slower, older peripherals, t he PCI
bus, and t he
AGP Bus.

The chipset cont rols t hese buses. It t ransf ers inf ormat ion t o and f rom t hem and t he processor
and memory. The chipset's capabilit ies in t his area det ermine what kinds of buses t he syst em
support s and how f ast t hey can get. For t his reason, Int el
calls it s chipset s "PCIset s". Most
modern PCs support t he ISA and PCI buses, but older chipset s support t he VESA Local Bus
inst ead of PCI.


Bus Bridges


A "bridge" is a net working t erm t hat ref ers t o a piece of hardware t hat connect s t wo dissimilar
net wor
ks and passes inf ormat ion f rom t he comput ers on one net work t o t hose on t he ot her,
and vice
-
versa. In t his way, t he chipset must use bus bridges t o connect t oget her t he dif f erent
bus t ypes it cont rols. The most common of t hese is t he PCI
-
ISA bridge, which
is used t o
connect t oget her devices on t hese t wo dif f erent buses.


IDE/ATA Hard Disk Cont roller


Almost all mot herboards now have support f or f our IDE (ATA) hard disks int egrat ed int o t hem,
t wo on each of t wo channels. Int egrat ing t his support makes sense

f or a number of reasons,
among t hem t he f act t hat t hese drives are on t he PCI bus, so t his saves an expansion slot and
reduces cost. The dat a t ransf er rat e of IDE drives is based on t heir using programmed I/O
(PIO) modes, and use of t he f ast est of t hese m
odes depends on support f rom t he PCI bus and
chipset. The abilit y t o set a dif f erent PIO mode f or each of t he t wo devices on a single IDE
channel, called
independent device timing
, is also a f unct ion of t he chipset. Wit hout t his
f eat ure, bot h devices must
run at t he speed of t he slowest drive.

More recent ly, ATA
-
33 drives have become t he t hing t o have. These enhanced IDE drives are
appealing mainly because of t heir at t ract ive price. Earlier chipset s only support ed PIO modes,
which required CPU involvement i
n every hard drive access. This isn't good when t rying t o
mult i
-
t ask. ATA
-
33 drives use DMA t o work wit hout CPU int ervent ion. This allows speeds of up
t o 33MBps. The concept of DMA is descibed below.


DMA Mode Support and Bus Mast ering


Direct memory acce
ss (DMA) provides a way f or devices t o t ransf er inf ormat ion direct ly t o and
f rom memory, wit hout t he processor's int ervent ion. It is st ill used by many devices, alt hough
newer t ransf er modes are now used f or high
-
perf ormance devices like hard disks. DMA is

cont rolled by t he chipset's DMA cont roller, and t he newer t he cont roller, t he more DMA modes
it s support s.

Bus mastering

is an enhancement of DMA whereby t he remot e device not only can send dat a t o
t he memory direct ly, it act ually t akes cont rol of t he bu
s, and perf orms t he t ransf er it self
inst ead of using t he DMA cont roller. This cut s down on t he overhead of having t he slow DMA
cont roller t alk t o t he device doing t he t ransf er, f urt her improving perf ormance. Bus mast ering
support is provided by t he chipset
.


USB & AGP Support


USB (Universal Serial Bus) is a new t echnology int ended t o replace t he current port s used f or
keyboards and mice. It is st ill unclear as t o whet her t his st andard will cat ch on and become
popular. USB has been around f or a while now,
alt hough it is st ill rat her rare t o see in act ion.
Despit e t his, most modern chipset s support USB.

AGP is anot her high
-
speed bus used f or graphics cards. This bus must be support ed by t he
chipset. The Int el 440LX used t o be t he only chipset t he support ed
it, but since t hen, many
more have emerged, including many not made by Int el.


Plug and Play


Plug and Play (PnP) is a specif icat ion t hat uses t echnology enhancement s in hardware, BIOSes
and operat ing syst ems, t o enable support ed devices t o have t heir sys
t em resource usage set
aut omat ically. Int ended t o help make inst allat ion easier by eliminat ing some of t he problems
wit h get t ing peripheral devices t o work t oget her, PnP requires support f rom t he chipset as
well.


Chipset s of f er support f or power manageme
nt on t he comput er. Most recent chipset s support a
group of f eat ures t hat reduce t he amount of power used by t he PC during idle periods. These
t ypes of f eat ures are deemed import ant f or a f ew reasons. First, many get concerned over t he
amount of power cons
umed by PC's when t hey are lef t on f or long periods of t ime. Secondly,
wit h t he use of lapt ops, many are concerned about t he lif e of t heir bat t ery.

Power management works t hrough a number of BIOS set t ings t hat t ell t he comput er when t o
shut down various p
ieces of hardware when it becomes idle. While, in t heory, t his is a good
idea, it does somet imes get in t he way. One example is t hat all
-
t oo
-
common wait t ime when
ret urning t o t he comput er t o wait f or t he hard drive t o power up. Somet imes, t he hard drive
w
ill power down t oo soon, and when you come back, you have t o wait a f ew seconds f or t he
drive t o power up again.

There are a number of t erms commonly heard in relat ion t o t hese power management f eat ures.
Energy Star

is a program st art ed by t he EPA t o bran
d PCs t hat are considered energy ef f icient
and incorporat e power management. Most modern PCs are Energy St ar compliant, and display
it s logo on t he t op of t he screen when t he BIOS boot s up.
Advanced Power Management

or APM
is t he name given t o t he componen
t in some operat ing syst ems (such as Windows 95) t hat
works wit h t he BIOS t o cont rol t he power management f eat ures of t he PC. APM allows you t o
set paramet ers in t he operat ing syst em t o cont rol when various power management f eat ures
will be act ivat ed.
Syst
em Management Mode

or SMM is a power
-
reduct ion st andard f or
processors. This allows t hem t o aut omat ically and great ly reduce power consumpt ion.


One of t he biggest issues wit h chipset s is what t ypes of memory t hey will support as well as
how much.

When p
urchasing a chipset, make sure you get one wit h support f or SDRAM. Wit h t his, 66MHz
is f ine f or most applicat ions, but wit h t he prices f or 100MHz chipset s coming down so much,
opt f or a chipset support ing t he 100MHz f ront side bus. You'll see t he dif f erence

in many
aspect s of t he comput er's use, especially t he more involved AGP
-
enabled applicat ions.

One needs t o pay at t ent ion t o how t he memory is support ed. A chipset can support a cert ain
amount of memory as well as is able t o cache a cert ain port ion of it.

This means t hat a cert ain
amount of t he main syst em memory will be cached by t he L2 cache, increasing perf ormance.
One of t he more f amous horror st ories is t he 430TX chipset by Int el. Alt hough it could support
up t o 256MB of SDRAM, it could only cache t he

f irst 64MB of it. This meant t hat wit h memory
amount s over 64MB, you were probably degrading t he syst em's perf ormance by quit e a bit.
Because Windows 95 loads it self int o t he higher memory areas, leaving t he lower areas f ree f or
DOS compat ibilit y, t his me
ant t hat t he OS and all syst em
-
crit ical applicat ions were being
hampered by t he crappy cache support.

When purchasing a chipset, make sure it can address 1MB or 2MB of L2 cache. Some come wit h
512K, which is adequat e, but don't consider 256K or lower. The

higher t he L2 cache, t he more
memory t he chipset is likely t o be able t o cache.

The chipset market will have t o evolve along wit h memory enhancement s. Minor t weaks t o
SDRAM, such as Double Dat e Rat e(DDR) SDRAM will ext end t he lif e of SDRAM, but will incl
ude
some t weaks t o t he chipset support. Int el's event ual move t o Rambus DRAM, or
RDRAM
, will
change everyt hing. While SDRAM delivers dat a st eadily at 66MHz of 100MHz, RDRAM will use
an 8
-
bit int erf ace and f ire dat a of f at 800MHz. Because of t he close int eg
rat ion of t he chipset
t o t he memory subsyst em, t he move t o RDRAM will require drast ic changes t o chipset design.


CMOS Backup Battery



The bat t ery in a PC is of t en one of t he most f orgot t en part s of t he comput er. It is quit e
import ant, t oo. It is what ho
lds all of your CMOS set t ings while your comput er is of f. Wit hout
it, you would have t o re
-
program your CMOS each and every t ime you t urned on your PC.


Expansion Cards



Expansion cards are t he small print ed circuit boards t hat you plug int o o
ne of t he slot s on your
mot herboard t hat make your comput er do "neat" t hings. They are video cards, sound cards,
modems, image capt ure cards, et c.

Expansion cards are one of t he simplest pieces of comput er hardware. You purchase your card
of choice, st ick
it in t he slot, and load t he new drivers.


Motherboard Slots

In order t o inst all an expansion card, you must st ick it int o one of t hose slot s on your
mot herboard. t here are dif f erent t ypes of slot s, alt hough only a f ew are st ill used t oday. Let's
look t hem

over.




Industry Standard Architecture (ISA):

This t ype of slot is t he oldest st ill in use
t oday. If you open up an old 286, you'll see a f ew of t hese. An 8
-
bit ISA slot is capable
of 0.625MB/sec t ransf er rat e bet ween t he card and t he mot herboard. Lat er v
ersions of
t his slot were 16
-
bit, capable of 2MB/sec. This is st ill slow compared t o t oday's
st andards, but cards such as modems do not require anyt hing f ast er t han t his. If you
look at your mot herboard's slot s, t he longer black ones are t he ISAs. If t hey
are all
one size, t hey are all ISAs. Modern boards are no boast ing any more t han maybe t wo
of t hese bad
-
boys, only because people only use t hem f or t heir modems or older cards
t hat haven't yet replaced.




Enhanced Industry Standard Architecture (EISA):

Thi
s t ype of slot is not used
very of t en in deskt op machines. It is used mainly in
servers
, or comput ers t hat host
net works. Wit h such a comput er, t he demands placed on it s component s are t oo big f or
ISA t o handle. Also, t he EISA bus is capable of
bus masteri
ng
, which allows
component s at t ached t o t he bus t o t alk t o each ot her wit hout bot hering t he CPU. This
f eat ure is much like SCSI and speeds up t he comput er quit e well.





Micro Channel Architecture (MCA):
Not t oo common eit her, t his bus was creat ed by
IBM. I
t is 32
-
bit, like EISA, but you can't st ick ISA cards int o it. MCA was capable of
bus mast ering, plus it could look at ot her devices plugged int o it and ident if y t hem,
leading t o aut omat ic conf igurat ion. MCA also produced less elect rical int erf erence,
redu
cing errors. MCA is hist ory. Don't get it. Nobody uses it.




Video Electronics Standard Association (VESA):
This is a very f ast int erf ace made
up mainly f or f ast new video cards. All of t hose f ancy videos and graphics require
much speed. The VESA
-
Local Bus
, or VL
-
Bus, is connect ed st raight t o t he CPU's own
int ernal bus, hence t he name "local". This bus can t ransf er dat a at 132MB/sec. VESA
buses are basically an ISA slot wit h an ext ra slot on t he end. The whole t hing is about
4 inches longer t han an ISA slot
. Again, you don't see t hese much anymore.




Peripheral Component Interconnect (PCI):

This is t he ot her very f ast bus
developed by Int el. It is dif f erent t han t he VL
-
Bus except t hat it runs at t he same
speed. There is a f ast int erf ace unit bet ween t he card

and t he CPU t hat does t he
t alking. This unit made t he bus independent of t he CPU, a drawback on t he VL
-
Bus,
which was limit ed t o t he 486. Also, you can plug cards int o it wit hout any conf iguring.
The bus is self
-
conf iguring, leading t o t he
plug
-
n
-
play

con
cept in which each add
-
on
card cont ains inf ormat ion about it self t hat t he processor can use t o aut omat ically
conf igure t he card. This slot is most popular t oday wit h Pent ium and lat er machines,
alt hough occasionally you will see one on a 486. If you're any
t hing like me, you never
have enough PCI slot s.




Personal Computer Memory Card International Association (PCMCIA):
This is a
special socket in which you can plug removable credit
-
card size devices. These circuit
cards can cont ain ext ra memory, hard drives
, modems, net work adapt ers, sound cards,
et c. Most ly, PCMCIA cards are used f or lapt ops, but many PC vendors have added
PCMCIA socket s t o t heir deskt op machines. The socket uses a 68 pin int erf ace t o
connect t o t he mot herboard or t o t he syst em's expansion
bus.

There are t hree t ypes of PC cards: Type 1 slot s are 3.3mm t hick and hold it ems such
as RAM and f lash memory. Type 1 slot s are most of t en seen in palmt op machines or
ot her handheld devices. Type 2 is 5mm t hick and I/O capable. These are used f or I/O
de
vices such as modems and net work adapt ers. Type 3 is 10.5mm t hick and used
mainly f or add
-
on hard drives. When buying PC Card equipment, you must consider t he
size of t he slot. In most cases, Type 3 can handle Type 2 and Type 1.


Accelerated Graphics Port

(AGP):

The newest t ype of bus slot creat ed f or t he high demands
of 3D graphical sof t ware. Since AGP is a hot t opic and t here is indeed much t o know.



Chapter 4

Memory

Your comput er's memory is necessary f or it s operat ion. It is f ully t ied in t o t he proc
essor,
chipset, mot herboard, and cache.


Memory Types



There are several dif f erent t echnologies available t oday when it comes t o memory. No longer
can you just buy a SIMM and st ick it in. There are many t ypes available. Let's discuss t hem
here.

ROM


This

is read
-
only memory, memory that can only be read, but cannot be written to. ROM is used in situations where the data must be
held permanently. This is due to the fact that it is non
-
volatile memory. This means the data is "hard
-
wired" into the ROM chip.
You
can store the chip forever and the data will always be there. Besides, the data is very secure. The BIOS is stored on ROM bec
ause the
user cannot disrupt the information.

There are dif f erent t ypes of ROM, t oo:



Programmable ROM(PROM)
. This is basically

a blank ROM chip t hat can be writ t en
t o, but only once. It is much like a CD
-
R drive t hat burns t he dat a int o t he CD. Some
companies use special machinery t o writ e PROMs f or special purposes.



Erasable Programmable ROM (EPROM)
. This is just like PROM, exc
ept t hat you can
erase t he ROM by shining a special ult ra
-
violet light int o a sensor at op t he ROM chip
f or a cert ain amount of t ime. Doing t his wipes t he dat a out, allowing it t o be rewrit t en.



Electrically Erasable Programmable ROM (EEPROM)
. Also called f
lash BIOS. This
ROM can be rewrit t en t hrough t he use of a special sof t ware program. Flash BIOS
operat es t his way, allowing users t o upgrade t heir BIOS.

ROM is slower t han RAM, which is why some t ry t o shadow it t o increase speed.

RAM


Random Access Memor
y (RAM) is what most of us t hink of when we hear t he word memory
associat ed wit h comput ers. It is volat ile memory, meaning all dat a is lost when power is t urned
of f. The RAM is used f or t emporary st orage of program dat a, allowing perf ormance t o be
opt imum.


Like ROM, t here are dif f erent t ypes of RAM:



Static RAM (SRAM)
. This RAM will maint ain it's dat a as long as power is provided t o
t he memory chips. It does not need t o be re
-
writ t en periodically. In f act, t he only t ime
t he dat a on t he memory is ref reshed o
r changed is when an act ual writ e command is
execut ed. SRAM is very f ast, but is much more expensive t han DRAM. SRAM is of t en
used as cache memory due t o it s speed.

There are a f ew t ypes of SRAM:



Async SRAM
. An older t ype of SRAM used in many PC's f or
L2

cache
. It is
asynchronous, meaning t hat it works independent ly of t he syst em clock. This
means t hat t he CPU f ound it self wait ing f or inf o f rom t he L2 cache.



Sync SRAM
. This t ype of SRAM is synchronous, meaning it is synchronized
wit h t he syst em clock. Wh
ile t his speeds it up, it makes it rat her expensive at
t he same t ime.



Pipeline Burst SRAM
. Commonly used. SRAM request s are
pipelined
, meaning
larger packet s of dat a re sent t o t he memory at once, and act ed on very
quickly. This breed of SRAM can operat e
at
bus

speeds higher t han 66MHz, so
is of t en used.



Dynamic RAM (DRAM)
. DRAM, unlike SRAM, must be cont inually re
-
writ t en in order
f or it t o maint ain it s dat a. This is done by placing t he memory on a ref resh circuit t hat
re
-
writ es t he dat a several hundred
t ime per second. DRAM is used f or most syst em
memory because it is cheap and small.

There are several t ypes of DRAM, complicat ing t he memory scene even more:



Fast Page Mode DRAM (FPM DRAM)
. FPM DRAM is only slight ly f ast er t han
regular DRAM. Bef ore t here

was EDO RAM, FPM RAM was t he main t ype used in
PC's. It is pret t y slow st uf f, wit h an access t ime of 120 ns. It was event ually
t weaked t o 60 ns, but FPM was st ill t oo slow t o work on t he 66MHz syst em bus.
For t his reason, FPM RAM was replaced by EDO RAM.
FPM RAM is not much
used t oday due t o it s slow speed, but is almost universally support ed.



Extended Data Out DRAM (EDO DRAM)
. EDO memory incorporat es yet
anot her t weak in t he met hod of access. It allows one access t o begin while
anot her is being complet ed
. While t his might sound ingenious, t he perf ormance
increase over FPM DRAM is only around 30%. EDO DRAM must be properly
support ed by t he chipset. EDO RAM comes on a SIMM. EDO RAM cannot operat e
on a bus speed f ast er t han 66MHz, so, wit h t he increasing use

of higher bus
speeds, EDO RAM has t aken t he pat h of FPM RAM.



Burst EDO DRAM (BEDO DRAM)
. Original EDO RAM was t oo slow f or t he
newer syst ems coming out at t he t ime. Theref ore, a new met hod of memory
access had t o be developed t o speed up t he memory. Burs
t ing was t he met hod
devised. This means t hat larger blocks of dat a were sent t o t he memory at a
t ime, and each "block" of dat a not only carried t he memory address of t he
immediat e page, but inf o on t he next several pages. Theref ore, t he next f ew
accesses w
ould not experience any delays due t o t he preceding memory
request s. This t echnology increases EDO RAM speed up t o around 10 ns, but it
did not give it t he abilit y t o operat e st ably at bus speeds over 66MHz. BEDO
RAM was an ef f ort t o make EDO RAM compet e w
it h SDRAM.



Synchronous DRAM (SDRAM)
. SDRAM is really t he new st andard f or PC
memory. It s speed is synchronous, meaning t hat it is direct ly dependent on t he
clock speed of t he ent ire syst em. St andard SDRAM can handle higher bus
speeds. In t heory, it can op
erat e at up t o 100MHz, alt hough it has been f ound
t hat higher qualit y
DIMM
s must be used f or st able operat ion at such speeds.
Hence
PC100 SDRAM
. Alt hough SDRAM is f ast er, t he speed dif f erence isn't
not iced by many users due t o t he f act t hat t he syst em cach
e masks it. Also,
many users are working on a relat ively slow 66MHz bus speed, which doesn't
use t he SDRAM t o is f ull capacit y. Using 100MHz chipset s, like t he BX and
ot her more modern chipset s, you can easily run your PC100 SDRAM at f ull
speed. Wit h some
newer chipset s by Via and ot hers, we now have PC
-
133 as
well.



RAMBus DRAM (RDRAM)
. Developed by Rambus, Inc. and endorsed by Int el
as t he chosen successor t o SDRAM. RDRAM narrows t he memory bus t o 16
-
bit
and runs at up t o 800 MHz. Since t his narrow bus t a
kes up less space on t he
board, syst ems can get more speed by running mult iple channels in parallel.
Despit e t he speed, RDRAM has had a t ough t ime t aking of f in t he market
because of compat ibilit y and t iming issues. Heat is also an issue, but RDRAM
has hea
t sinks t o dissipat e t his. Cost is a major issue wit h RDRAM, wit h
manuf act urers needing t o make major f acilit y changes t o make it and t he
product cost t o consumers being t oo high f or people t o swallow.

DDR
-
SDRAM
. This t ype of memory is t he nat ural evolut io
n f rom SDRAM and most
manuf act urers pref er t his t o Rambus because not much needs t o be changes t o make it. Also,
memory makers are f ree t o manuf act ure it because it is an open st andard, whereas t hey would
have t o pay license f ees t o Rambus, Inc. in order m
ake RDRAM. DDR st ands f or Double Dat a
Rat e. PC
-
100 and PC
-
200 DDR
-
SDRAM bot h use t he 100 MHz bus speed, but DDR shuf f les dat a
over t he bus over bot h t he rise and f all of t he clock cycle, ef f ect ively doubling t he speed. Of
course, chipset support is necessa
ry, but Via, ALi, and Micron have already decided t hey will
support DDR
-
SDRAM in t heir chipset s rat her t han RDRAM.


SDRAM Considerations


SDRAM is t he new st andard in PC memory, t he next st ep beyond t he now ancient EDO RAM.
But, in buying SDRAM f or you sys
t em, t here is some inf ormat ion you must consider.



Speed


SDRAM chips are generally named in t wo dif f erent ways. The most common way is t he
nanosecond rat ing. It is said t o have a "10 nanosecond" rat ing, which is t he common speed f or
SDRAM. The second me
t hod is t he MHz rat ing, like "100 Mhz".

SDRAM is synchronous, meaning it is t ied int o t he bus speed of t he syst em. This means t hat
t he memory must be f ast enough t o work on t he syst em you int end t o put it on. Unlike older
memory

t hat used
wait states

t o c
ompensat e f or slowness, SDRAM does not use wait st at es. The
memory, t hen, must be f ast enough f or t he syst em, t aking slack int o account.

It is really t his reason why SDRAM was creat ed in t he f irst place: t o make memory t hat could
keep up wit h t he syst em.
For older syst ems, EDO RAM does just f ine. At t he 66MHz speed, EDO
is a dream, as t hat is what it was really designed f or. It was soon f ound t hat EDO RAM worked
just f ine at even higher speeds, such as 75MHz or 83MHz. SDRAM was designed mainly t o
operat e w
it h st abilit y at bus speeds such as 100MHz. The problem wit h t his is t hat, unt il more
recent ly, we really had very f ew mot herboards t hat could make it t o 100MHz. Theref ore, how
are we t o know t hat t hat expensive SDRAM will really do it?

In modern syst ems,

f ast er bus speeds are t he norm. EDO RAM will not work wit h st abilit y, if at
all, in t hese syst ems. SDRAM is t hus used. PC
-
100 SDRAM is used in 100MHz syst ems. Newer
PC
-
133 is used on 133MHz syst ems.


2
-
clock vs. 4
-
Clock


Two types of SDRAMs are the 2
-
clo
ck and the 4
-
clock. Structurally, they are the same, but they are accessed differently. A 2
-
clock
SDRAM module is set up so that each clock cycle accesses two chips on the module. A 4
-
clock SDRAM setup accesses 4 chips per
clock cycle. To choose what kind
to get, you must look into the motherboard's documentation. 4
-
clock modules seem to be the popular
choice.


Serial Presence Detect


Some SDRAM modules have a special EEPROM chip on it t hat holds inf ormat ion about t he
SDRAM module, such as speed set t ings.
The mot herboard t hen queries t his chip f or inf o and
makes changes in t he set t ings t o work wit h t he SDRAM. Basically, t his allows t he SDRAM
module and t he chipset t o communicat e, making t he SDRAM more reliable on a larger number
of mot herboards. Some mot her
boards require t his f eat ure. You will have t o look at t he manual,
once again. If your board requires it, make sure you have it, because SDRAM wit hout t his
won't work.

When choosing SDRAM f or your comput er, you need t o know your mot herboard and get exact ly

t he t ype it requires


SDRAM, PC100, PC133, and DDR


PC
-
100

We all know t hat, when it comes t o memory, t hat SDRAM is t he way t o go. It is f ast er t han
EDO RAM, and support s higher bus speeds. EDO RAM is moving int o t he older syst ems, mainly,
while even t he
bargain PC's make t he move t o SDRAM.

But, t he world of SDRAM is not cut and dry. St andard SDRAM is great f or "older" boards. Now,
wit h t he release of BX mot herboards, and t he Super 7 boards, st andard SDRAM begins t o cause
problems. Why? Because even t houg
h it was originally said t hat SDRAM could go up t o 100MHz,
it really couldn't. In f act, some SDRAM even got unst able at t he 83MHz bus speed.

Ent er PC100. Basically, PC100 is SDRAM which meet s a cert ain specif icat ion t o work wit h
st abilit y at 100MHz. This
SDRAM usually operat es at 10ns, alt hough some is creat ed t hat is
f ast er. Since t he only qualif icat ion f or PC100 is t he abilit y t o operat e at 100MHz, t here is no
rule as t o t he access t ime. 10ns is t he minimum speed f or st abilit y at 100MHz. some companies
a
dvert ise PC100 f ast er t han t his, say 6ns, but, a lot of t imes you will f ind t his t o be
inaccurat e.

All PC100 is not equal. While it all operat es at 100MHz, when you get int o higher bus speeds
t han t hat, t he high
-
qualit y st uf f st art s t o st and out. The reas
on is t hat t he lat ency rat ing of
t he higher qualit y st uf f is lower. The lat ency is a measurement of how long it t akes f or ot her
hardware t o ret urn dat a t o t he RAM. The lower t he lat ency rat ing, t he bet t er t he chip, and t he
f ast er it will operat e.

The most

common, and cheaper, t ype of SDRAM chip uses GL or G8 chips. The "GL" or "G8" will
be seen on t he act ual SDRAM chips on t he memory circuit board, so you will know what you're
looking at. The GL's use a CAS lat ency of 3, which is pret t y st andard. The bet t e
r st uf f uses
"GH" chips, which uses a CAS lat ency of 2.

To operat e at 100MHz or 112MHz bus speeds, almost any of t his PC100 will work. But, bump it
up t o 133MHz, and you'll need t o get t he bet t er GH SDRAM wit h a CAS lat ency of 2. Only wit h
t his will you g
et st able operat ion at such high
front side bus

speeds.

Along wit h high qualit y PC100, one must t ake not ice of t he print ed circuit board on which t he
chips are mount ed. The qualit y of t hese boards, f or t he most part, is measured in t he amount
of layers. Y
ou can equat e t his t o t hickness. Obviously, t he t hicker t he mat erial of t he board,
t he less chance you have of damaging it, t he longer it will last, and t he less elect rical noise
you will get. so, t he more layers t he bet t er. Run
-
of
-
t he
-
mill, cheap SDRAM of
t en used good
qualit y chips, but t he manuf act urer would cut corners by using lower qualit y PCB's(Print ed
Circuit Boards). Of t en t hey would use 4
-
layer PCB's. Well, part of t he PC100 spec is a minimum
of 6
-
layer PCB. t his ensures a higher level of qualit y.
But, some manuf act urers use even bet t er
PCB's, such as 8
-
layer. Pay at t ent ion t o t his. The more layers t he bet t er.

So, if you f ind yourself buying a Super 7 or BX mot herboard, you should pick up some PC100
SDRAM wit h it. The older st uf f will work, but, wi
t hout PC100, you are st uck wit h your new
board's slower bus speeds.


PC
-
133

Basically, PC133 SDRAM is anot her implement at ion of t he same old SDRAM. It's basically t he
same SDRAM f rom t he days of t he LX Chipset, t he Pent ium II 333MHz processor, and t he
66M
Hz bus. The only dif f erence bet ween PC133 SDRAM and t he ot hers, is t hat t he PC133 has a
lower
latency

t han PC100 and PC66 SDRAM, which means it can run on a f ast er bus.

If you don't already know, PC133 SDRAM can run st ably on a 133MHz bus, just as PC100 r
an
st able on t he 100MHz bus, and PC66 ran st able on t he 66MHz bus. PC133 SDRAM increases t he
t ot al bandwidt h available t o t he processor f rom t he memory, because it runs f ast er. That is
because it raises t he speed limit, so t o speak, on t he road bet ween t he

Processor and t he RAM.

Somet imes it easy t o t hink of t he lines dat a moves bet ween t wo comput er component s as
roads. The road bet ween t he SDRAM and a current processor, like t he Pent ium III, is 64bit,
which can be t hought of as a 64 lane highway. Wit h old
er PC100 SDRAM, t he speed limit on
t hat road was 100MHz, which means t hat during a second, 100 million bit s moved t hough each
lane on t he highway. That's 6.4 Billion bit s, and as we all know, 8 bit s = 1 byt e. That means,
t hat wit h older PC100 SDRAM, t he pr
ocessor could get a maximum of 800MB per second. Wit h
PC133 SDRAM, t he speed of t hat road is increased t o 133.33 million bit s on each lane per
second. That t ranslat es int o 8.533 bill bit s. Using t he same mat h above, t hat means t he
processor could get a max
imum of 1060 MB per second (1.06GB) f rom t he SDRAM.

More dat a, of course, means bet t er perf ormance. Your games will run f ast er, business
applicat ions load f ast er, and even Windows boot s f ast er. Only problem is t hat t he perf ormance
increase isn't all t hat
much, and most of t he t ime it's hardly not iceable. Possibly wit h new
t ypes of SDRAM which are t rying t o compet e wit h
RamBus RAM
, users will see a much higher
perf ormance increase.

Double Data Rate

Well, t here really is not much t o say on t his t opic, becau
se t he t opic is rat her cut and dried.
DDR RAM is Normal SDRAM t hat sends dat a bot h on t he rising of t he clock cycle, and t he
f alling of t he clock cycle.

Twice t he sending of t he dat a, t wice t he dat a sent. Where st andard 100 MHz SDRAM has an
est imat ed 800
MB/sec dat a t ransf er rat e f or a t heoret ical maximum, DDR is, not surprisingly,
t wice t hat. No, we don’t act ually see t hat much bandwidt h, but t hat is t heir t heoret ical
maximum (64 bit X 100 MHz = 800 MB/s). DDR SDRAM would be 1600 MB/s. It s just f ast er, an
d
it will be cheaper t han Rambus RAM, and it s current ly support ed by quit e a f ew mot herboard
manuf act urers.

Chapter 5

Video Cards


The video card cont rols t he qualit y of what you see on your monit or. It cont ains all t he
circuit ry necessary f or displaying

graphics. It usually is a separat e card t hat f it s int o one of
your mot herboard's slot s, but somet imes t his circuit ry is incorporat ed int o t he mot herboard
it self.

When buying a new video card it is very import ant t o "mat ch" it t o your monit or. If you've g
ot
a f ancy new video card and a puny monit or, you just won't be able t o view t he wonders of your
card t hat you paid good money f or. It is a good idea t o buy t he video card f irst, t hen buy a
suit able monit or. Bet t er yet, buy t he monit or and t he card as a se
t so t hey will be perf ect ly
mat ched.


Accelerated Graphics Port


Today's sof t ware is increasing in graphics int ensit y. Even "mundane" business sof t ware uses
icons, chart s, animat ions, et c. When you add 3D games and educat ional sof t ware t o t he
equat ion, one

can see t hat t here is a crunch in bandwidt h f or graphical inf ormat ion. Wit h
newer sof t ware and games get t ing much more graphics int ensive, t he PCI bus is maxed out. In
f act, t he PCI bus, once considered very f ast, can now be considered a bot t leneck.

Int e
l knew t his. In response, t hey designed t he Accelerat ed Graphics Port, or AGP. Int el
def ines AGP as a "high perf ormance, component level int erconnect t arget ed at 3D graphical
display applicat ions and is based on a set of perf ormance ext ensions or enhanceme
nt s t o PCI."
In short, AGP uses t he main PC memory t o hold 3D images. In ef f ect, t his gives t he AGP video
card an unlimit ed amount of video memory. To speed up t he dat a t ransf er, Int el designed t he
port as a direct pat h t o t he PC's main memory.

AGP sounds

groundbreaking, and it is, no doubt, t he lat est craze in t he need f or graphical
speed. One reason it is f ast er t han PCI is t hat, while PCI runs at 33MHz, t he AGP bus runs
much f ast er. A 4X AGP bus runs at 4 t imes 33MHz, or 133MHz! Also, a normally clocked

PCI bus
can achieve a t hroughput of 132MB/s. Yes, t his is f ast, but when compared t o t he t hroughput s
of 3D games, one f inds t hat it is not enough. AGP, running in 2x mode (2 x 33 = 66MHz), can
achieve a t hroughput of 528MB/s! AGP pulls t his of f by const an
t ly t ransf erring dat a on bot h
t he rises and f alls of t he 66MHz clock cycle. Also, AGP makes use of sideband t ransf ers and
pipelining

so it can const ant ly t ransf er dat a wit hout depending on ot her component s in t he PC.

The
pipelining

abilit y of t he AGP bus
is a key point t hat explains why it provides a perf ormance
advant age. Since AGP pipelines operat ions it can process quicker and more ef f icient ly t han PCI
bus can. AGP uses a special organizat ion process f or all pending and processing request s. In
ef f ect, t
he bus can process one inst ruct ion while st ill recieving t he next inst ruct ions. This
allows much more t o be accomplished in a short er amount of t ime.

For a diagram of how t he AGP bus is st ruct ured, see
this diagram

provided by
Intel Corporation
.

One can
easily see why t he need f or a new graphical int erf ace is needed. While PCI served us
well, and st ill cont inues t o do so, it is bogged down by t he demand of f ull screen 3D graphics.
It works great f or 2D business sof t ware and most games, but int ense 3D chal