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PCI 2.3 and 5V signaling (was: PCI-X Compatibility)

PCI Revision 2.3 eliminates 5V plug-in cards, but does NOT eliminate 5V PCI motherboards.

Prior to PCI Revision 2.3, this is what we had:
- Two kinds of PCI buses (or motherboards or system boards): 5V or 3.3V.
- Three kinds of PCI plug-in cards: 5V-only, 3.3V-only, or Universal.

PCI Revision 2.3 eliminates only the 5V-only PCI plug-in cards.

PCI Revision 2.3 continues to support 5V buses (motherboards), into which any Universal plug-in card or Revision 2.1 or 2.2 compliant 5V-only card can be plugged.

If this caught you by surprise, then I don't know where you've been hiding.  The writing has been on the wall for years.  Since 1995, the PCI Spec has been saying that everyone should be designing only Universal plug-in cards.  Yet it amazes me how many people still keep designing 5V-only plug-in cards in 2002 ... seven years later!

The PCI SIG has struggled for years with this problem.  Corelogic (motherboard) chipsets have had a hard time maintaining 5V compatibility in order to support these ancient technology 5V-only cards that keep being designed and manufactured.

Would you prefer that computer vendors simply start introducing systems with 3.3V PCI buses (because they can't make corelogic chipsets that can receive 5V signals), and instantly invalidate millions of 5V-only PCI plug-in cards that are already out there?  Or would you prefer to have years of warning, and a phase-in of requirements that 5V-only cards shouldn't be made anymore because this transition to 3.3V buses inevitably must happen, and you'd better not get caught out in the cold making 5V-only cards?  I'm glad the PCI SIG mandated this.  I'm just surprised it didn't happen a lot sooner.

Technology is the driving force.  But PCI plug-in cards haven't kept up with technology.  They are slow and have gotten by with 1990 IC processing technologies.  Corelogic chipsets can't afford to do that.  So you're going to see 5V PCI buses disappearing from motherboards, not because the PCI Spec says so (it doesn't!), but because they just can't make them anymore.  5V-only PCI plug-in cards had better be scarce when that happens, or there will be a major technology disruption.

Andy