PCIe x1 -> 3 x1 or more switching chipsets in cMP?

Discussion in 'Mac Pro' started by William_si, Apr 4, 2016.

  1. William_si macrumors regular

    William_si

    Joined:
    Apr 4, 2016
    Location:
    Croatia
    #1
    I have ordered one of these which are listed as "OSX compatible":

    http://www.ebay.com/itm/221692418838

    This thing splits x1 PCIe coming from the wifi card slot into 3 x1 slots at supposedly PCIe 2.0 with being specification compliant, likely done by some PCIe switching chip (also indicated by price).

    Does anyone use something like this currently or can provide other input?
    Mine should arrive in some days (SG post is fast these days to EU) so i'll be able to provide some data.
     
  2. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
    #2
    What do you want to achieve with this?
    In all cMPs mini PCIe slot is 2.5GT/s (PCIe 1,1) x1 with max real throughput ~200MB/s.
     
  3. William_si thread starter macrumors regular

    William_si

    Joined:
    Apr 4, 2016
    Location:
    Croatia
    #3
    Where does a 4,1/5,1 even get a 1.1 lane from, the PCH and CPU(s) should be 2.0 only?

    No specific plans, i add it with some power from the SATA cabling into the DVD bay which nicely fits 2 x1 -> x16 risers on bottom (even with height difference for the mounting) and this expander/switch on top with some space left for power cabling. Fun project.

    If the expander for some reason does not work i connect one x16 riser again to mini PCIe directly and run an additional x4 dual port Intel LAN @ x1 which even at 1.0/1.1 should be almost non-oversubscribed.
     
  4. h9826790 macrumors 604

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #4
    From the south bridge.
    Screen Shot 2015-05-15 at 19.13.16.png
     
  5. William_si thread starter macrumors regular

    William_si

    Joined:
    Apr 4, 2016
    Location:
    Croatia
    #5
    Very helpful, thanks!
     
  6. William_si thread starter macrumors regular

    William_si

    Joined:
    Apr 4, 2016
    Location:
    Croatia
    #6
    So as update, i have this card now and as expected it is a PLX chip on it.

    From spec sheet it seems to be x1 1.1/2.0 to 3x x1 1.1/2.0 with a shared bus, the chip is compatible with the cMP chipset though does not acknowledge any card behind it currently.

    I try to figure out if this happens due to me expanding 2x x1 to 2x x16 and not use it direct (unlikely, used before from Mini PCIe without PLX), issue with Mini PCIe (worked before with just extender to x16), lack of power in SATA bay (unlikely) or SW support (unlikely, network card not seen in Win 10 either).

    Pics of install of 2 x16 expanders in the SATA bay with this expander in use:

    https://imgur.com/a/sK0Z0
     
  7. p.l macrumors member

    p.l

    Joined:
    Jun 3, 2015
  8. William_si thread starter macrumors regular

    William_si

    Joined:
    Apr 4, 2016
    Location:
    Croatia
    #8
    Semi.

    The chip should work, the card says it has a PCIe link (which due to lack of EFI shell/kernel debugger i cannot see, need to boot a Linux) but a x4 dual Gbit network card (Intel, works in Slot 1-4 and extended mini PCIe) is not detected.

    Will later test with an x1 card or two.
     

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