concerns about dual 1.8

Discussion in 'Buying Tips, Advice and Discussion (archive)' started by Bhennies, Dec 26, 2004.

  1. Bhennies macrumors 6502

    Mar 20, 2004
    NYC & Baltimore
    Hi all, first of all, I know this question was addressed a while back, but I can't find it in a search (the search engine on this site is awful). Anyway, here goes.

    I'm ready to buy a refurb dual 1.8 (after MWSF...but I'm not holding my breath about new g5's), and I have a major concern.

    PCI vs PCI-X.

    I don't care about the speed of the bus or's just that there seems to be a lot of misinformation about the standard and compatibility specs on the internet and I thought maybe I could get a definitive answer here.

    I've already had to sell my g4 desktop and digi 001 because of PCI compatibility issues with the g5's. As I understand it, the voltage is different.

    If I buy a new dual 1.8, will most future PCI-X cards be incompatible with the PCI on the DP 1.8? If it's just a regular PCI slot, why couldn't my digidesign PCI card work with it? The only thing I can think of is that it may be a higher voltage PCI slot and thus NOT a normal PCI slot but also NOT pci-x????

    I am looking into buying a lynx 2 mastering converter PCI interface soon. Assuming it works with the dual 2.0 and 2.5 (I know it does), will it work with the dual 1.8?

    sorry for the confusion....

    Thanks for the reply and if someone is an archive digger and has found a prior thread discussing this topic, please point me to it.
  2. Sun Baked macrumors G5

    Sun Baked

    May 19, 2002
    The current PCI and PCI-X slots use the same keyed 3.3V PCI slot.

    PCI runs at 66MHz

    PCI-X runs and 100MHz and 133MHz

    PCI-X 2.0 will run at 200 and 266MHz

    All the first rev. A PowerMacs had a HT PCI-X Tunnel, some just ran it at PCI speeds (the PCI variant machines.)

    The Rev. B G5 PowerMacs dropped the HT PCI-X Tunnel in the PCI version and are sharing the PCI bus on the southbridge chips (K2 in the DP, consumer Shasta chip in the SP.)


    Even though they can all use PCI cards, they all share the same quirk that was intoduced with the XServe -- the older 5V PCI cards are null and void.

    In fact if you run a 5V PCI card in the XServe G4 it tended to destroy the motherboard.

    Xserve: Won't Turn on After PCI Cards Are Installed

    Edit: So yes it is just a bandwidth and clock issue between PCI and PCI-X on the G5s and XServe G4 -- they all need 3.3V cards.

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