The Video Graphic Adaptor Expansion Card (VGA card)
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Whenever any kind of display is to be connected to the computer
then there must be a VGA card inside. A PC, as an end user machine,
always has a graphic card but there are computers that do not need
it: print servers, routers, and stuff like that.
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Matrox Millennium G450 graphic adaptor (AGP), front view
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Because the graphic adaptor needs to have certain speed priorities in
the computer system, it is almost impossible to run two of them in one
machine. Hence, if more than one monitor is to be run on one computer,
a so-called Dual Head VGA card must be used, that is, a
graphics adaptor equipped with two VGA plugs, as the Matrox G450
(pictured above and below) is one.
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VGA cards differ in their performance and in the kind of bus / kind
of slot they use.
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The performance depends mainly on three things:
- the graphic processor (graphic chip)
There are certain chips that are good for games (high
3D-performance, rendering, aliasing) like the VooDoo
chip series, and there are others that are good for
Computer Aided Design (CAD) like the G450. For office
use all modern chipsare good enaugh.
- the amount of graphic memory
This determines which graphic solution of the screen can
be displayed at what color depth, because on the graphic
card's RAM all information about the next screen to show
is stored.
There should be at least 4 MB of video memory on
the card. If a 14-inch-monitor is used, 1 MB or
2 RAM is also fine, because it would not display
high resolutions anyway
- the speed of graphic memory
It determines how many frames per second can be transmitted
to the monitor (refresh rate). The refresh rate
should be at least 70 Hz for convenient and ergonomic
working.
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Matrox Millennium G450 graphic adaptor (AGP), back view
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VGA's must use a system bus for data transmission from and to
the CPU. The following solutions are common:
- ISA bus
Too slow nowadays. Though there are still ISA cards in use,
for the graphics adaptor a more modern solution should be
chosen.
- VL bus
In some 386 and 486 Intel PC's there is a bus called
Vesa Local. It is not state of the art anymore, but
if there is a VL graphics card present, it should suffice.
- PCI bus
PCI is a bus that is in every respect fast enaugh to transmit
graphic information. In praxis, however, PCI graphic adaptors
are either slow and outdated, or they are very expensive.
For the middle-of-the-road end user there are no more PCI-VGA's
developed today.
- AGP bus
Almost all modern PC's nowadays come along with an AGP slot.
This AGP slot can only accomodate graphic adaptors, so if there
is AGP in the system, one should use it for the VGA rather
than "wasting" a PCI slot for the graphic adaptor.
AGP cards are the best choice for graphics, and they are,
moreover, often cheaper than their according "PCI versions".
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