 |
 |
 |
 |
 |
 |
Graphics Cards
Graphics cards, or video cards, are necessary on all computers that wish to display an image on a screen. Every modern computer has one, but the size and capability varies enormously. Let's start by looking at the 3 main types of card available.
- PCI
- AGP
- PCI Express
PCI Graphics Cards
The letters 'PCI' stand for Peripheral Component Interconnect, and is the term used to describe a bus that connects components directly to the system's memory and to the system's processor through the 'frontside bus'. When discussing communications on a motherboard, the term 'bus' has nothing to do with the vehicle that takes the kids to school. There may be several buses in a computer, and like the PCI bus, they are all responsible for managing the communication 'traffic' from different devices to the processor. An example of a PCI graphics card is shown below.
 |
The frontside bus is a high speed connection that manages the processor's communication with items such as hard drives, memory, and PCI devices, while not burdening the processor with all of the management responsibilities.
First developed by Intel in the early 1990s, PCI was spawned from even earlier (and slower) bus architectures such as ISA (Industry Standard Architecture) and VL-Bus (VESA Local), which were common back in the 1980s and 1990s.
A 64-bit PCI card features 184 pins for mating with the appropriate slot on a system's motherboard, but can generally fit into a 32-bit slot as well, as long as features on the motherboard do not interfere. When installed in a 32-bit slot, data transfer on a 64-bit card will be limited to 32-bit. The Intel STL2 Dual Socket 370 Server Board is a good reference for comparing 32-bit and 64-bit PCI slots. Looking at the lower left corner of the motherboard shows four 32-bit PCI slots and two 64-bit PCI slots. |
Although the different format PCI cards may be interchangeable, PCI, AGP, and PCI Express cards do not work (or fit) in any other type of slot. Most PCI cards will be of the 32-bit variety, and the selection of items available is fairly extensive. Graphics cards, sound cards, network cards, RAID controllers, TV tuners, modems, and USB/Firewire controllers are all common items that may be added to a system through the use of a PCI card.
The PCI slot has been around for a while, and seems to have a place in at least the near future of computer architecture. AGP and PCI Express offer performance benefits that the PCI standard cannot match, but for many applications, the performance offered by PCI is more than adequate.
Having said that, with the advent of AGP and PCI Express cards, PCI cards are becoming increasingly difficult to get hold of. There are some specialist companies that still make one, but the chances are that when you go out to buy a new one, you will find plenty of AGPs and PCI Expresses in the shops, and not many PCIs.
| <<< Previous page |