[ The PC Guide | Systems and Components Reference Guide | Video Cards | Video Card Performance ]

System Interface

The interface (normally meaning the system bus) that the video card uses to connect to the rest of the PC has an important impact on performance. Due to the large amount of data that flows between the video card and other parts of the system, the type and speed of system bus used can limit the performance of a video card. Many video cards come in versions for different buses; in particular some come in a PCI version and a VLB version, where the chipset and memory are the same and only the bus interface differs. These can differ in speed, although PCI and VLB both in general provide comparable performance. However, you can take that same chipset and put it on the ISA bus and the performance will degrade a lot, because the ISA bus is only 16 bits wide and very slow.

The frequency that the system bus runs at is also important. The PCI bus on a standard PC can range in speed from 25 to 33 MHz; obviously the video card running at 33 Mhz will be faster than the one running at 25. The key issue here is the bandwidth of the system bus. Higher bandwidth buses support faster video cards. See here for more details on system bus bandwidth.

Next: Relationship to the Processor and Other Components

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