The new revision requires motherboard and PC card suppliers to eliminate support for 5-volt-only PCI cards. The new specification should have little impact on the industry, one analyst said, because the older 5V cards make up only a tiny fraction of todays devices.
The Peripheral Connection Interface—which serves as the foundation for the PCI 66, PCI-X, Mini PCI and Low Profile PCI used in PCs, embedded devices and servers—serves as computings backbone. PCI add-on cards, which include sound, graphics, storage I/O and other devices, replaced the ISA bus in the 1990s.
While PCI 2.3 allowed motherboards to use cards with either 3.3V or 5V interfaces, the new revision will force card makers to design 3.3V-only devices. Although the initial PCI specification allowed 5V cards, the SIGs roadmap always called for the evolution to 3.3V-only cards, said Tony Pierce, a technology evangelist for Microsoft Corp. and the chairman of the PCI SIG.
"We have had the migration path to 3.3V cards in place since day one in 1992," Pierce said. "At the time, market demands didnt deem it necessary to transition. Now, everyone is on board. I would be very surprised if anyone is designing new 5V cards, but there is an installed base to consider. We have already seen a transition away from 5V, as most 3.3V cards we see today are 5V-tolerant."
PCI cards are "keyed" with notches to prevent PCI cards from being used with the wrong voltages. But recently, chip designers have begun to forego the 5V interface to simplify the chip itself and lower its cost.
The question is just how many old 5V cards remain inside old PCs and servers. "What I have worked with only supports 3.3V," said Dean McCarron, principal analyst at Mercury Research in Cave Creek, Ariz. "The only support for 5V-only that Ive seen is in embedded products."
He said most of the graphics cards hes worked with, including those using chips from Nvidia Corp. or ATI Technologies Inc., used only 3.3V cards.
"Very few 5V cards—almost none—exist at this point in the server space, but I cannot speak for the PC market," sad Al Yanes, the president of the PCI SIG and a senior technical staff member for IBM in its Engineering & Technology Services Group.
"Most people are getting away from 5V because of the reduced power consumption. PCI SIG has been actively supporting and promoting the move to 3.3V for more than five years. This is a natural progression for the spec that is expected by the industry."