2| 1. Defining Memory

jaspersugarlandSoftware and s/w Development

Dec 14, 2013 (3 years and 7 months ago)

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Chapter 7, Memory



Instructor Note

Students will learn about the different types of memory in this chapter.
Ensure that students understand the different meanings of the term
memory
. Allow about
65

80 minutes to cover all slides in this chapter.

Lesson 1
defines the different types of memory and explains how to expand or add new
memory. Allow about 25

30 minutes for Slides 1

7 (pages 120

26 of the textbook) and
about 20

25 minutes for Slides 8

9 (pages 127

33).

Lesson 2 explains hexadecimal notation and me
mory allocation. Allow about 20

25
minutes for this lesson.

The supplementary student Lab Manual contains a lab that can be used to reinforce the
learning from this chapter. In this lab, students will remove and replace a single inline
memory module (SIMM)
. In your classroom presentation, be sure to stress the importance
of protecting delicate electronic components from electrostatic discharge (ESD).

For the classroom presentation, plan to have an open system nearby to demonstrate
memory module removal and

replacement to students before they do the lab. If possible,
have newer dual inline memory modules (DIMMs), as well as the older 30
-
pin and 72
-
pin
SIMM modules. In addition, be prepared to demonstrate the MEM.COM command with
the /C switch and the /P swit
ch (Slide 13).





Instructor Note

Use Slide 1 to introduce the two lessons in this chapter.


|1|

Chapter Overview


A.

ROM and RAM

B.

Memory Mapping


Chapter 7, Lesson 1


ROM and RAM

|2|

1.

Defining Memory



Instructor Note

When explaining the term “memory,”

ensure that students understand the
difference between memory and storage. Computer users frequently use the two terms
incorrectly.



A.

Definition of memory: the area within a computer where information is
stored while being worked on



1.

Information is
stored by using on or off switches, where on = 1

and off = 0.


2.

When strung together, these switches can represent large numbers and
code values.

2

Outline,
Chapter 7


ALS: A+ Certification, Third Edition

|3|

2.

Nonvolatile and Volatile Memory




Instructor Note

Use Slide 3 to explain the two major classes of memory. To clarify the
classes of memory, you can use this analogy. Compare your computer to an office that
contains a desk and a set of file cabinets. The file cabinets represent the computer’s hard
disk, w
hich provides high
-
capacity storage. The desk represents memory, which offers
quick and easy access to the files you are working with at the moment. Make sure students
understand that the information stored on a hard disk remains intact even when the
compu
ter is turned off, as opposed to data held in volatile memory that is cleared when the
computer is turned off. (It’s like saying that any files left on the desk at closing time will be
thrown away.)


A.

Computer memory includes two major classes: nonvolatile

and volatile.

B.

Nonvolatile memory


1.

Retains data even when the computer power is shut off


2.

Example: setup data in complementary metal
-
oxide semiconductor
(CMOS)


C.

Volatile memory


1.

Loses data when the power is shut off


2.

Example: data held in e
lectronic memory

|4|

3.

Read
-
Only Memory (ROM)



Instructor Note

When you present Slide 4, emphasize that the computer uses ROM to store
permanent configuration information. Point out that this information is retained when the
computer is shut down.


A.

Nonvolatile memory that is generally installed during manufacturing


B.

Protects the information required to start and run the computer


C.

Holds instructions for performing the power
-
on self test (POST) and
basic input/output system (BIOS) information


D.

Requires attention only if it needs to be replaced or upgraded

|5|

4
.

Random Access Memory (RAM)



Instructor Note

Ensure that students understand the difference between ROM and RAM.
Point out that all information in RAM is lost when the computer is shut down.

Explain the different types of memory used in computers. Explain that
refreshing
is the
process used to rest
ore the charge in dynamic RAM (DRAM) memory cells at specified
intervals that do not depend on the system clock (asynchronous). Contrast DRAM and
synchronous DRAM (SDRAM). SDRAM differs from earlier types in that it does not run
asynchronously to the syste
m clock the way older, conventional types of memory do. The
clock that controls the microprocessor also controls the SDRAM, thereby eliminating wait
states and reducing data retrieval times.

Explain the use of parity for checking memory errors. Discuss me
mory banks, but
emphasize that 72
-
pin SIMMs and DIMMs include an entire bank on a single chip.


Outline,
Chapter 7

3

ALS: A+ Certification, Third Edition

A.

A form of volatile memory that holds temporary instructions and data for
manipulation while the system is running


B.

Includes the following common variations:


1.

DRAM


a.

Uses a microscopic capacitor and transistor to hold data


b.

Charged capacitor = 1, discharged capacitor = 0


c.

Capacitor holds a charge for a fraction of a second and then releases it.


d.

The process of recharging these capacitors is called

refreshing
.


2.

SDRAM


a.

Newer memory technology


b.

Permits support for higher bus speeds than DRAM does


C.

Parity


1.

Is a method of ensuring data integrity


2.

Adds an extra bit (called the
parity bit
) to each 8
-
bit
bus cycle
(transaction between th
e CPU and memory)

3.

Two kinds: even and odd


D.

Error
-
correction coding (ECC)


1.

Is more robust than the parity method


2.

Detects errors by adding more information about the bits


E.

Access speed


1.

Is the amount of time in nanoseconds (ns) that it takes
RAM to provide
the requested data to the memory controller

2.

Ensure that add
-
on memory is the same speed as, or faster than, existing
memory.

3.

Do not mix memory modules with different speeds in the same
bank
(the
row of slots for adding memory).


4.

Check the

motherboard specifications for the required speed.

|6|

5.

RAM Packaging


Instructor Note

Use Slide 6 to discuss the different ways memory is packaged. Discuss the
older memory types

dual inline package (DIP) and single inline pinned package (SIPP)

on through the newer SIMMs and DIMMs. When you discuss DIMMs, introduce the term
banking
. You sh
ould mention that there are newer technologies than this. Kingston
Technology Inc. makes 184
-
pin RIMM 64
-
MB, 128
-
MB, and 256
-
MB modules with very
fast bus transfer speeds (800 MHz).



A.

DIP


1.

Obsolete technology


2.

Chips were added one at a time.



B.

SIPP


1.

Obsolete technology


2.

A printed circuit board with individual DRAM chips mounted on it


3.

Very fragile and easily damaged

4

Outline,
Chapter 7


ALS: A+ Certification, Third Edition


C.

SIMM


1.

Is easier to install than a SIPP


2.

Is similar to a SIPP, but does not require pins


3.

Most common vers
ions in PC: 30
-
pin and 72
-
pin


4.

Handle it properly to reduce the risk of damage from ESD.


D.

DIMM


1.

One card forms a complete bank.


2.

Used on new motherboards


3.

Easy to install

|7|

6.

Memory Configuration


Instructor Note

Explain the term
banking

again and emphasize the examples on page 125 of
the textbook. Explain the following: Because DIPs support 8 bits each, a 32
-
bit processor
would require four banks because the processor is capable of processing 32 bits at a time.

A 64
-
bit processor would
require 4 banks of 16 bits each.



A.

8
-
bit data bus requires memory in 8
-
bit chunks.


1.

DIP: 8 pieces


2.

SIPP: 1 piece


B.

16
-
bit data bus requires memory in 16
-
bit chunks.


1.

DIP: 16 pieces


2.

SIPP: 2 pieces


3.

30
-
pin SIMM: 2 pieces


C.

32
-
bit data

bus requires memory in 32
-
bit chunks.


1.

DIP: not applicable


2.

SIPP: 4 pieces


3.

30
-
pin SIMM: 4 pieces


4.

72
-
pin SIMM: 1 piece


5.

DIMM: 1 piece

|8|

7.

Installing SIMMs


Instructor Note

Use Slide 8 to discuss the general steps in installing SIMMs. St
udents will
install SIMMs in the Lab Manual lab that supports this chapter. Also, discuss some basic
troubleshooting methods for memory after installation.



A.

Before installing SIMMs, check the voltage of the memory module.


1.

Early PCs used 5
-
volt circ
uits.


2.

The current trend is to use 3.3
-
volt power.


B.

When installing SIMMs


1.

Use ESD protection and handle SIMMs carefully.


2.

The notch in the SIMM prevents improper installation.


3.

Insert the SIMM at a 45
-
degree angle along the wide side.

Outline,
Chapter 7

5

ALS: A+ Certification, Third Edition


4.

A
fter the SIMM is securely seated, push it upright until it clicks into
place.


C.

After installing the SIMM


1.

Turn on the computer and verify the new memory value.


2.

If the RAM value has not changed, the SIMM might not be installed
correctly, or a bank

might be disabled.


3.

If the computer does not boot, the RAM was not installed correctly.

|9|

8.

Cache Memory


Instructor Note

Use Slide 9 to emphasize that the memory hierarchy is built so that the
fastest memory is closest to the CPU and the slower memory is further away from the CPU.

Explain the term
cache

and the layers of caching. Mention that the L1 cache is located
inside

the processor itself and is the most efficient way for the processor to access code.
Explain that the L2 cache is located outside the processor.

Ensure that students understand caching is not limited exclusively to electronic memory.
For example, there a
re different types of caches (such as the Web page cache in Microsoft
Internet Explorer) that store information on the hard disk drive.

You can use this analogy to help students understand cache memory. Suppose you need to
write a term paper on the Americ
an Revolutionary War. You go to the library and search
for books on the subject. You select three or four books, take them home, and start on your
term paper. You don’t need to check out all the books in the library at once. In the same
way, computer progr
ams do not access all of their data at one time.


A.

Caching refers to holding recently or frequently used code or data in a
special memory location for rapid retrieval.

B.

Static RAM (SRAM)


1.

Is the high
-
speed memory chip generally used for caching


2.

Uses
a special circuit called a flip
-
flop rather than capacitors


3.

Is fast and does not need to be refreshed


4.

Is more expensive than DRAM


C.

Caches are organized into layers to keep the necessary data as close
as possible to the CPU.


1.

The internal cach
e (L1) receives all commands for the CPU.


2.

The external cache (L2) can be added or expanded.


3.

A write
-
through cache sends all data directly to RAM.


4.

A write
-
back cache stores data for a time and sends it to RAM later.


6

Outline,
Chapter 7


ALS: A+ Certification, Third Edition


Chapter 7, Lesson 2

Memory
Mapping

|10|

1.

The Workings of Hexadecimal Code


Instructor Note

Briefly review the binary concepts students learned in Chapter 2. To build
on these concepts, explain that hexadecimal notation (also known as hex) is well
-
suited for
addressing memory since

it can be easily translated to binary. Review the examples shown
on Slide 10.

If time permits, use the following example. Consider the hex number AA. It can be written
in the more explicit form of A*(16
1
) + A*(16
0
), which is one way to convert a hex numbe
r
into a decimal number. In this case, A*(16
1
) equals decimal 160 (A=10), and A*(16
0
)
equals decimal 10 (any number raised to the power of 0 is 1), resulting in the formula
160+10=170. AA in hex equals 170 in decimal. Notice that it takes eight binary digi
ts

10101010

to write the binary equivalent of 170 (decimal), but it takes only two hex
numbers. This is one reason that hex is so efficient for mapping memory

hexadecimal is a
shortcut for expressing binary numbers.


A.

Hexadecimal notation is a numbering sys
tem based on 16 instead

of 10.

B.

Hexadecimal simplifies the notation of binary code.

|11|

2.

Memory Allocation

a


Instructor Note

Use Slide 11 to explain how memory is allocated to processes running on
the CPU. Emphasize the differences between extended and expanded memory, and between
real mode and protected mode.



A.

Conventional memory: this limit is only significant to MS
-
DOS
a
pplications and does not apply to applications for Microsoft Windows
95 and later versions.


B.

Reserved memory: the first 640 KB is reserved for the operating

system (OS).


C.

Upper memory: 384 KB of RAM is earmarked for computer
housekeeping (for exampl
e, BIOS and video RAM).


D.

High memory area (HMA) is the first 64 KB of extended memory.


E.

Extended memory versus expanded memory: Microsoft Windows
applications used extended memory, and expanded memory is only
significant to MS
-
DOS.

F.

Real mode versus p
rotected mode


1.

In real mode, an application expects full control of the system.


2.

Protected mode allows multiple applications to run at once.

|12|


G.

Shadow RAM

a


Instructor Note

Use Slide 12 to discuss the use of the reserved memory area for shad
owing.


Outline,
Chapter 7

7

ALS: A+ Certification, Third Edition


1.

Rewrites BIOS contents into upper memory area


2.

Dramatically increases speed when application software calls BIOS
routines


|13|

3.

Determining Usable Memory


Instructor Note

Use Slide 13 to discuss and demonstrate the command
-
line command
ME
M.COM with the /C switch. Emphasize that this command is generally used with MS
-
DOS and Microsoft Windows 3.
x

to determine available conventional and upper memory
area (UMA) memory for use by device drivers and terminate
-
and
-
stay
-
resident (TSR)
programs.

Y
ou may want to demonstrate using MEM /P, a MEM.COM switch that is not covered in
the textbook but is very useful. When using the command with the /P switch, point out the
hexadecimal addresses that indicate what part of memory a specific process is loaded
into.



A.

The MEM.COM command provides the following:


1.

Information about the amount and type of memory available


2.

A quick way to determine how all memory areas are being used and the
total amount of RAM active in the system


B.

Switches used with ME
M.COM


1.

MEM /C allows you to determine which device drivers and TSR
programs are loaded.


|14|

Chapter Summary


A.

The two basic kinds of computer memory are ROM (nonvolatile) and
RAM (volatile).


B.

RAM is packaged in a variety of designs, including DIP
s, SIPPs,
SIMMs, and DIMMs.


C.

Installing SIMMs requires ESD protection and careful handling.


D.

Cache memory enhances computer performance.


E.

Hexadecimal code simplifies the notation of binary code.


F.

Memory allocation was complex in MS
-
DOS but is s
implified in
Windows.