Graphics - Prof. M. Saeed

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2 Δεκ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Computer Graphics

Prof. Muhammad Saeed

2

Hardware

( Graphic Cards )

II


Hardware II
Computer Graphics

1 August 2012

3

With a
PCI
-
based

graphics
card, every texture map has to
be stored twice. First, the
texture map is loaded from the
hard drive

to the system
memory (
RAM
) until it has to be
used. Once it is needed, it is
pulled from memory and sent to
the CPU to be processed. Once
processed, it is sent through the
PCI bus to the graphics card,
where it is stored again in the
card's
framebuffer
. All of this
storing and sending between
the system and the card is very
draining to the overall
performance of the computer.


Hardware II
Computer Graphics

PCI(Peripheral Component Interface
)

1 August 2012

AGP(
Accelerated Graphics Port

)

Card

4

AGP is built on the idea of
improving the ways that PCI
transports data to the CPU. Intel
achieved this by addressing all
of the areas where PCI transfers
were causing data bottlenecks
in the system. By clearing the
traffic jams of data,
AGP
increases the speed

at which
machines can render graphics
while using the system's
resources more efficiently to
reduce overall drag.


Hardware II
Computer Graphics

It achieves the goal by:

1 August 2012

5

1. Dedicated Port



There are no other devices connected to the AGP other

than the graphics card. With a dedicated path to the CPU,

the graphics card can always operate at the maximum

capacity of the connection.


2. Pipelining



This method of data organization allows the graphics card

to receive and respond to multiple packets of data in a

single request. Here's a simplified example of this:


With AGP, the graphics card can receive a request for all of

the information needed to render a particular image and

send it out all at once. With PCI, the graphics card

would receive information on the height of the image and

wait... then the length of the image, and wait... then the

width of the image, and wait... combine the data, and

then send it out.



Hardware II
Computer Graphics

1 August 2012

6

3.
Sideband addressing



Like a letter, all requests and information sent from one part

of your computer to the next must have an address

containing "To"

and "From." The problem with PCI is that

this "To" and "From" information is sent with the

working

data all together in one packet. This is the equivalent of

including an address card inside the envelope when you

send a letter to a friend: Now the post office has to open the

envelope to see the address in order to know where to send

it. This takes up the post office's time. In addition, the

address card itself takes up room in the envelope, reducing

the total amount of stuff you can send to

your friend.


With sideband addressing, the AGP issues eight additional

lines on the data packet just for addressing. This puts the

address on the outside of the envelope, so to speak, freeing

up the total bandwidth of the data path used to transfer

information back and forth. In addition, it

unclogs system

resources that were previously used to open the packet to

read the addresses.


Hardware II
Computer Graphics

1 August 2012

7



AGP: Saves RAM

AGP improves the process of storing texture maps by
allowing the
Operating System

to designate RAM for
use by the graphics card on the fly. This type of
memory is called
AGP memory

or non
-
local video
memory. Using the much more abundant and faster
RAM used by the operating system to store texture
maps reduces the number of maps that have to be
stored on the graphics card's memory. In addition, the
size of the texture map your computer is capable of
processing is no longer limited to the amount of RAM
on the graphics card.




Hardware II
Computer Graphics

1 August 2012

8

AGP saves RAM is by only storing texture maps
once. It does this with a little trickery. This trickery
takes the form of a chipset called the
Graphics
Address Remapping Table (GART).

GART takes the
portion of the system memory that the AGP
borrows to store texture maps for the graphics
card and re
-
addresses it. The new address
provided by GART makes the CPU think that the
texture map is being stored in the card's frame
buffer. GART may be putting bits and pieces of the
map all over the system RAM; but when the CPU
needs it, as far as it's concerned the texture map is
right where it should be.

GART


Hardware II
Computer Graphics

1 August 2012

PCI (
Peripheral Component Interconnect
)
Express Card

9

PCI Express is a serial
connection that operates more
like a network than a
bus
.
Instead of one bus that handles
data from multiple sources,
PCI
-
e has a switch that controls
several point
-
to
-
point serial
connections. These connections
fan out from the switch, leading
directly to the devices where
the data needs to go. Every
device has its own dedicated
connection


Hardware II
Computer Graphics

1 August 2012

10

Each lane of a PCI Express
connection contains two pairs of
wires
--

one to send and one to
receive. Packets of data move
across the lane at a rate of one bit
per cycle. A
x1 connection
, the
smallest PCI
-
e connection, has
one lane made up of four wires. It
carries one bit per cycle in each
direction. A x2 link contains eight
wires and transmits two bits at
once, a x4 link transmits four bits,
and so on. Other configurations
are x12, x16 and x32.

PCI Express Lanes


Hardware II
Computer Graphics

A x16 PCI
-
e connector can move 6.4 GB
of data per second in each direction
.

1 August 2012

11

Computer Graphics

The

video BIOS

or

firmware

contains the basic
program, which is usually hidden, that governs
the video card's operations and provides the
instructions that allow the computer and
software to interact with the card. It may contain
information on the memory timing, operating
speeds and voltages of the graphics processor,
RAM, and other information.

Video BIOS

1 August 2012

Hardware II

12

Computer Graphics

Graphics Processing Unit (GPU )

A
GPU

is a dedicated processor optimized for accelerating
graphics. The processor is designed specifically to
perform

floating
-
point

calculations, which are fundamental to
3D graphics rendering and 2D picture drawing. The main
attributes of the
GPU

are the core

clock frequency, which
typically ranges from 250

MHz to 4

GHz and the number of
pipelines (
vertex


and
f ragment


shaders), which translate a 3D
image characterized by vertices and lines into a 2D image
formed by

pixels.

Modern
GPU
s are massively parallel, and fully programmable.
Their computing power is orders of magnitude greater than that
of CPUs for certain kinds of operations. This has led to the
emergence of

general
-
purpose computing on graphics
processing units (
GPGPU
).

Occasionally called

visual processing unit

or

VPU
.

1 August 2012

Hardware II

13

Computer Graphics

Compute Unified Device Architecture(CUDA)

CUDA

is a parallel computing architecture developed by

Nvidia

for
graphics processing.
CUDA

is the computing engine in
Nvidia

graphics processing units

(GPUs) that is accessible to
software developers through variants of industry standard
programming languages.


CUDA

gives developers access to the virtual

instruction set

and
memory of the

parallel computational

elements in
CUDA

GPUs.
Using
CUDA
, the latest
Nvidia

GPUs become accessible for
computation like

CPUs. Unlike CPUs however, GPUs have a parallel
throughput architecture that emphasizes executing many
concurrent threads slowly, rather than executing a single thread
very quickly. This approach of solving general purpose problems on
GPUs is known as

GPGPU
.

1 August 2012

Hardware II

14

Computer Graphics

Power demand

As the processing power of video cards has increased, so
has their demand for electrical power. Current high
-
performance video cards tend to consume a great deal of
power. While CPU and

power supply

makers have recently
moved toward higher efficiency, power demands of GPUs
have continued to rise, so the video card may be the
biggest electricity user in a computer.

Although power
supplies are increasing their power too, the

bottleneck

is
due to the

PCI
-
Express

connection, which is limited to
supplying 75 Watts.

Modern video cards with a power
consumption over 75 Watts usually include a combination
of six
-
pin (75W) or eight
-
pin (150W) sockets that connect
directly to the power supply.

1 August 2012

Hardware II

15

Computer Graphics

High
-
Definition Multimedia Interface
(HDMI)



High
-
Definition Multimedia Interface (HDMI)

An advanced digital audio/video interconnect released in
2003 and is commonly used to connect

game
consoles

and

DVD players

to a display. HDMI supports
copy protection through

HDCP(High
-
bandwidth Digital
Content Protection) .

1 August 2012

Hardware II

16

END

Hardware II


16


Hardware II
Computer Graphics

1 August 2012