CertiGuide to A+ (Core Hardware)  9  Chapter 0001:  Power Supplies - System Board       9  XI  Expansion Buses

VESA Local Bus (VLB) 1 XII  Plug and Play

Once again, looking back at our brief history tour in Chapter 0000, it was revealed that Intel ended the bus wars for a number of years by releasing the Peripheral Component Interconnect (PCI) expansion bus.

The original PCI bus was similar in design to VLB. With the advent of PCI Version 2.0, it was no longer a local bus, as it got its own data path, and designed to be independent of the CPU design. Most PCI buses operate at 33Mhz, offering a 32-bit bus using 124 pins. The extra pins are used for power and grounding.

Adaptec has been the champion of a 64-bit PCI bus, utilizing 188-pins, and being backwards compatible with regular PCI by extending the slot, just as in 8-bit to 16-bit ISA. Not many manufacturers of PC equipment have jumped on the 64-bit PCI bandwagon promoted by Adaptec, although it is seen in data communications equipment. Because this card is so rare, take a look at one below, compared to a ‘regular’ PCI card. (At least this way you can say you have seen one).

While Adaptec has not been entirely successful with creating a market standard for 64-bit PCI, the point they are making has not gone unnoticed. Advances in RAM, CPUs and even storage have reached the point where the once waiting for other sub systems are close to saturating the PCI bus. To that end, look for PCI-X.

VESA Local Bus (VLB) 1 XII  Plug and Play