Evaluating Hardware: Supplemental Information

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3 Δεκ 2013 (πριν από 3 χρόνια και 8 μήνες)

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Clock Speed

http://www.pccomputernotes.com/clockspeed/clockspeed.htm

The clock speed of a CPU is defined as the frequency that a processor executes instructions or that data
is processed. This clock speed is measured in millions of cycles per second or megahertz (MHz). The
clock itself is actually a quartz crystal that vibr
ates at a certain frequency when electricity is passed
through it. Each vibration sends out a pulse or beat, like a metronome, to each component that's
synchronized with it.

Tablet Computers

http://tabletnat
ion.com/compare#


Machine cycle

http://www.webopedia.com/TERM/I/instruction_cycle.html

The time period during which one
instruction

is fetched from
memory

and executed when a
computer

is
given an instruction in
machine language
. There are typical
ly four stages of an instruction cycle that the
CPU

carries out:

1.

Fetch

the instruction from memory. This step brings the instruction into t
he
instruction register
,
a circuit that holds the instruction so that it can be decoded and executed.

2.

Decode the instruction.

3.

Read the effective address from memory if the instruction has an indirect address.

4.

Execute

the instruction.

Steps 1 and 2 are called the
fetch cycle

and are the same for each instruction. Steps 3 and 4 are called
the
execute cycle

and will change with each instruction.

The term refers to both the series of four steps an
d also the amount of time that it takes to carry out the
four steps.

An instruction cycle also is called
machine cycle
.

Cache

http://computer.howstuffworks.com/cache.htm

If you have been shopping for a
computer
, then you have heard the word "cache." Modern computer
s
have both L1 and L2 caches, and many now also have L3 cache. You may also have gotten advice on the
topic from well
-
meaning friends, pe
rhaps something like "Don't buy that Celeron chip, it doesn't have
any cache in it!"

It turns out that caching is an important computer
-
science process that appears on every computer in a
variety of forms. There are memory caches, hardware and software d
isk caches, page caches and more.

Front side bus

http://computer.howstuffworks.com/motherboard4.htm

Bus speed usually refers to the speed of the
front side bus

(FSB), which connects the CPU to the
northbridge. FSB speeds can range from 66 MHz to over 800
MHz. Since the CPU reaches the memory
controller though the northbridge,
FSB speed can dramatically affect a computer's performance
.

Solid state drive

http://en.wikipedia.org/wiki/Solid
-
state_drive

A
solid
-
state drive

(
SSD
), sometimes called a
solid
-
state
disk

or
electronic disk
, is a
data storage device

that uses
integrated circuit

assemblies as
memory

to store data
persistently
. SSD te
chnology uses
electronic interfaces compatible with traditional block I/O hard disk drives. SSDs do not employ any
moving mechanical components, which distinguishes them from traditional
magnetic disks

such as
hard
disk drives

(HDDs) or
floppy disk
, which are
electromechanical

devices containing spinning
disks

and
movable
read/write heads
.
[1]

Compared to electromechanical disks, SSDs are typically less susceptible to
physical shock, are si
lent, have lower
access time

and
latency
, but are more expensive per unit of
storage
.

The data transfer rate is commonly used to measure how fast data is transferred from one location to
another. For example, a hard drive may have a maximum data transfer rate of 480 Mbps, while your ISP
may offer an Internet connection with a maximum data

transfer rate of only 1.5 Mbps.

Data Transfer Rate

http://www.techterms.com/definition/datatransferrate

Data transfer rates are typically measured in bits per second (bps) as opposed to bytes per second,
which can be understandably confusing. Because ther
e are eight bits in a byte, a sustained data transfer
rate of 80 Mbps is only transferring 10MB per second. While this is confusing for consumers, Internet
service providers must enjoy measuring data transfer rates in bps since it makes their Internet acce
ss
speeds sound 8x faster than they really are.

Blu
-
Ray disks

http://en.wikipedia.org/wiki/Blu
-
ray_Disc

Blu
-
ray Disc (official abbreviation BD) is an optical disc storage medium designed to supersede the DVD
format. The plastic disc is 120 mm in diameter
and 1.2 mm thick, the same size as DVDs and CDs. Blu
-
ray
Discs contain 25 GB[ambiguous] per layer, with dual layer discs (50 GB) being the norm for feature
-
length video discs. Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD
-
X
L re
-
writer drives.[2]


The major application of Blu
-
ray Discs is as a medium for video material such as feature films. Besides
the hardware specifications, Blu
-
ray Disc is associated with a set of multimedia formats. Generally these
formats allow for the
video and audio to be stored with greater definition than on DVD.

Definition of: shared video memory

http://www.pcmag.com/encyclopedia_term/0,2542,t=shared+video+memory&i=51248,00.asp


Using part of main memory for the display system's frame buffers, whic
h temporarily hold the rendered
content being sent to the screen. Shared memory is typically used in PCs with "integrated graphics,"
which means the display circuits are on the
motherboard

rather than housed in a separate, more costly
display adapter card.


Sharing main memory with the display function reduces the amount of memory available to
applications, and main memory is not as fast as the specialized
video

memory on stand
-
alone cards (see
video RAM
). See
integrated graphics

and
display adapter
.

Definition of: video RAM

Also called
"VRAM," it is the type of memory used in a display adapter. Video RAM is
designed with dual ports so that it can simultaneously refresh the screen while text and
images are drawn in memory. It is faster than the common DRAM or SDRAM chips used as
main memo
ry in the
computer
.

Color/Bit depth

http://en.wikipedia.org/wiki/Color_depth

In
computer graphics
,
color depth

or
bit depth

is the number of
bits

used to indicate the
color

of a
single
pixel

in a
bitmapped

image or video
frame buffer
. This concept is a
lso known as
bits per pixel

(bpp), particularly when specified along with the number of bits used. Higher color depth gives a
broader range of distinct colors.

Graphics Processing Unit

http://www.webopedia.com/TERM/G/GPU.html

Used primarily for
3
-
D

applications, a graphics processing unit is a single
-
chip processor that creates
lighting effects and transforms objects every time a
3D

scen
e is redrawn. These are mathematically
-
intensive tasks, which otherwise, would put quite a strain on the
CPU
. Lifting this burden from the CPU
frees up
cycles

that can be used for other jobs.

Sound Card

Analog vs. Digital

http://computer.howstuffworks.com/sound
-
card1.htm

Sounds and computer data are fundamentally different. Sounds are analog
-

they are made of waves
that travel through
matter. People hear sounds when these waves physically vibrate their eardrums.
Computers, however, communicate digitally, using electrical impulses that represent 0s and 1s. Like a
graphics card, a sound card translates between a computer's digital informa
tion and the outside world's
analog information.

The most basic sound card is a printed circuit board that uses four components to translate analog and
digital information:



An analog
-
to
-
digital converter (ADC)



A digital
-
to
-
analog converter (DAC)



An ISA or
PCI interface to connect the card to the motherboard



Input and output connections for a microphone and speakers

Instead of separate ADCs and DACs, some sound cards use a coder/decoder chip, also called a CODEC,
which performs both functions.