SLI working on Mac Pro

Discussion in 'Mac Pro' started by sasquatch98, Aug 23, 2006.

  1. ampd macrumors regular

    ampd

    Joined:
    Jan 10, 2006
    #2
    This is great news! Hopefully we will be getting the drivers to do this in OSX...
     
  2. MovieCutter macrumors 68040

    MovieCutter

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    May 3, 2005
    Location:
    Washington, DC
    #3
    Kick ass. I wonder if this would work with two PC GPUs? Dual x1950's here I come!!!
     
  3. ezekielrage_99 macrumors 68040

    ezekielrage_99

    Joined:
    Oct 12, 2005
    #4
    Does the SLI just only work with Windows or does Mac OSX supports this as well?
     
  4. Felldownthewell macrumors 65816

    Felldownthewell

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    Location:
    Portland
    #5
    Wow, those are some impressive 3dmark result jumps!
     
  5. ksz macrumors 68000

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    Oct 28, 2003
    Location:
    San Jose, CA
    #6
    Fantastic! I didn't know there were chipset-neutral drivers for SLI!! Wow!
     
  6. aiongiant macrumors 6502a

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    Aug 8, 2006
  7. Lollypop macrumors 6502a

    Lollypop

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    Johannesburg, South Africa
    #8
    Cool! Now all apple has to do is write the drivers.. or have ATI and nvidia write the drivers... 2009 anyone? :D
     
  8. cw2k macrumors newbie

    Joined:
    Feb 22, 2006
    #9
    Just Windows, when you boot back into OSX the cards function as 2 separate cards as they would normally do.

    The driver works with 7900/7600/7300 cards (does not work with 7950GX2).

    Newer drivers have not been modified yet as NVidia has put in integrity checks to prevent this type of mod working.

    Source of the driver: http://www.xtremesystems.org/forums/showthread.php?t=106212

    I will do further tests later today.
     
  9. Spanky Deluxe macrumors 601

    Spanky Deluxe

    Joined:
    Mar 17, 2005
    Location:
    London, UK
    #11
    This is outstanding news!! 2x7300gt cards is a quite reasonable mid range solution performance and cost wise.

    An SLI connector isn't required by the latest of nVidia drivers anyway - I found that out by losing my connector in my PC for months. I thought I'd left it at home when I went for Uni. When I was packing up my stuff to come back I found it behind the computer. Doh!

    Not having an SLI connector is more of a bottleneck on high end cards but on low end cards it doesn't make much of a difference.

    Edit: CW2K, welcome to MacRumors btw! Are you a poster over at xtreme? I used to be but got burnt by destroying two processors with a phase change system so have left the xtreme tweaking to the pros now. Could you run any benchmarks? Lost coast for example? High res?

    Edit 2: Also do those drivers support coolbits and can you try overclocking the cards a bit? They appear to be quite well designed 7300s so they could maybe be overclocked a bit. Overclocking 7300s seem to give a great boost in performance: http://www.techspot.com/review/6-geforce_7300gt_sli_performance/
     
  10. Mr. Mister macrumors 6502

    Joined:
    Feb 15, 2006
    #12
    Very interesting but it's a shame there isn't slotspeed configuration where there are two 16x's and the rest are something really low, the highest you can get two slots to go right now is 8x.
     
  11. ksz macrumors 68000

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    Oct 28, 2003
    Location:
    San Jose, CA
    #13
    In SLI configuration, I believe nVidia's cards only use 8 lanes each.
     
  12. godbout macrumors regular

    Joined:
    Jun 22, 2005
    Location:
    Montreal, Canada
    #14
    I don't know about that because I am not sure that crossfire has chipset independent drivers

    Dual 7950GTX here I come!!! ;)
     
  13. godbout macrumors regular

    Joined:
    Jun 22, 2005
    Location:
    Montreal, Canada
    #15
    I don't think that there are enough PCI-e lanes for quad SLi on the macpro chipset... well not 4X8 anyways...

    your options are:

    Slot 1 Slot 2 Slot 3 Slot 4
    Option 1 8-lanes 8-lanes 1-lane 8-lanes
    Option 2 8-lanes 8-lanes 4-lanes 4-lanes
    Option 3 16-lanes 1-lane 1-lane 8-lanes


    (I think)
     
  14. godbout macrumors regular

    Joined:
    Jun 22, 2005
    Location:
    Montreal, Canada
    #16
    No if you have a Nvidia chipset that supports SLi then you can have 2 16x lanes that will be used for the two graphics cards.

    http://www.slizone.com/page/slizone_learn.html
     
  15. CyberPrey macrumors regular

    Joined:
    Aug 10, 2006
    Location:
    IGH, MN
    #17

    nForce 4 chipset...

    My gaming rig has one of those... the mainboard is Asus A8N32-SLIDeluxe nForce4 SLI - Dual 16x PCI-E slots for the vid cards.
     
  16. ksz macrumors 68000

    Joined:
    Oct 28, 2003
    Location:
    San Jose, CA
    #18
    It's a little more complicated than that. AnandTech has an explanation of SLI here. The second paragraph states:

    The takeaway message I believe is:

    1. All PCIe graphics cards require x16 *physical* slots. This is simply the specification for any graphics card.
    2. Not all PCIe slots are *electrically* x16. This is limited by the chipset. Most chipsets do not allow two 16-lane electric configuration.
    3. The MacPro has 5 PCIe slots. They are all physically x16 slots, but not electrically. If all 5 slots were electrically x16, the total lanes would have been too many for the chipset to handle.
    4. Because Apple wants to allow multiple graphics cards in order to support multiple monitors, and because all PCIe graphics cards require x16 *physical slots*, all 5 of the MacPro's slots are physically x16.
    5. However, only 1 slot can be set electrically to x16.
    6. This is not limited to Apple's motherboard. Most PC motherboards are also limited to one *electrical* x16 slot.
    7. If you put two graphics cards in the MacPro, one of them will use at most eight electric lanes. The real-world impact of this is negligible as indicated by AnandTech. The difference between 16 electric lanes and 8 isn't anything to worry about.
    8. Finally, nVidia supports the following electric lane configurations for SLI:
    • x8 and x8 (officially)
    • x16 and x2 (unofficially)
     
  17. CyberPrey macrumors regular

    Joined:
    Aug 10, 2006
    Location:
    IGH, MN
    #19
    #8, That is incorrect. Check both Asus and nvidia's websites.

    Nvidia fully supports a 16x/16x SLI configuration on the NForce 4 SLI Chipset.

    I haven't read the spec's fully in a while, but in order to use a 16x/16x SLi setup, both the northbridge AND southbridge dedicate lanes to each card... 16x physically AND electrically...
     
  18. ksz macrumors 68000

    Joined:
    Oct 28, 2003
    Location:
    San Jose, CA
    #20
    ^^^ You're right about the A8N32-SLI motherboard and the nForce4. AnandTech's article is dated November 2004 at which time x16/x16 was not supported. What is interesting, though, is that the MacPro supports x8/x8, which has only a "negligible" hit on performance.
     
  19. CyberPrey macrumors regular

    Joined:
    Aug 10, 2006
    Location:
    IGH, MN
    #21
    I'm only right about 1 or 2 times a year :)

    While I 'think' i will be happy for quite some time using 1 16x card in the Mac Pro, I have a feeling that there will probably be some sort of change in the Apple computer line that DOES allow for 2 16x graphics cards to be used.
     
  20. ksz macrumors 68000

    Joined:
    Oct 28, 2003
    Location:
    San Jose, CA
    #22
    One third of the year is still left; looks like you may be improving your batting average!

    I wasn't expecting SLI to work at all, so the fact that it actually does and that it is supported by these el cheapo 7300GTs is something to get excited about. Do two 7300GTs equal one X1900XT? Or at least come close?
     
  21. topgunn macrumors 65816

    topgunn

    Joined:
    Nov 5, 2004
    Location:
    Texas
    #23
    Thats a reasonable question. What does a X1900 or even a 7900GT or GTX (non-SLI) score in 3D Mark '06?
     
  22. DougTheImpaler macrumors 6502a

    Joined:
    Feb 28, 2006
    Location:
    Central Illinois
    #24
    No, but you get two things instead:

    1.) Save $200 over an X1900XT
    2.) Shorter shipping delay than the X1900XT

    All told, they're probably about as fast as a single 7600GT or 7600GS, which is still a better gaming option than the X1600's in the iMac
     
  23. topgunn macrumors 65816

    topgunn

    Joined:
    Nov 5, 2004
    Location:
    Texas
    #25

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