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PCI-X Backplane 2u?

Discussion in 'Electronic Design' started by yy7d6, Aug 31, 2006.

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  1. yy7d6

    yy7d6 Guest

    Hi i am designing a board that will connect to a pci-x single board
    computer directly (without backplanes) via PICMG 1.0 edge connector in
    the sbc, problem is that IDSEL is not direcly available on the Card
    Edge Pins, the PICMG 1.0 Specification tells that IDSEL1's must be
    routed with AD31 for backplane slot 1, IDSEL2 with AD30 etc. right?
    and btw, what does 2U in PCI-X Backplanes means?

  2. Paul Burke

    Paul Burke Guest

    No idea about PCI-X, but 2U is a height measurement of about 3.5 inches.
  3. Eeyore

    Eeyore Guest

    2U means 2 units of 19" rack equipment height. 3.5 inches.

  4. Ben Jackson

    Ben Jackson Guest

    Normally during a command cycle all of the targets look at AD0..31 (or
    up to 63 for 64 bit) to decide if the address falls within their mapped
    space(s). However, if the command is config read or config write, then
    it looks exclusively at IDSEL and AD0..1 to decide if it's selected.
    Then, within the config space, only the lower address bits are used
    because the config space is small. For that reason, many bridge
    chipsets use AD16..31 as IDSEL lines, connecting them to the individual
    slots. That's not required by the spec, it's just a common feature
    of PCI bridge chipsets.
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