GeForce 8800 GTX "OC" running on Mac Pro

Discussion in 'Mac Pro' started by barefeats, Feb 7, 2008.

  1. macrumors 65816


    Jul 6, 2000
    I just installed Vista Ultimate 64 in the Boot Camp generated partition of a 8-core Mac Pro 3.2GHz. Then I pulled the Radeon HD 2600 XT out and replaced it with a PC compatible BFG nVidia GeForce 8800 GTX (768MB - overclocked) --- which, by the way, requires two power feeds. Thankfully I had two proprietary power cords from Apple and the motherboard has two 6 pin power feeds.

    The GeForce 8800 GTX booted up just fine with Vista as the default boot volume. I've installed the latest driver from nVidia. It's running at 2560x1600 on the 30" Cinema.

    Next I'm going to run some gaming benchmarks and report back. Moo ha ha.
  2. macrumors 6502a

    Feb 6, 2008
    The Netherlands
    I wonder... Is it possible to have two GPU's, one for use in Windows and one for OSX? I mean, can you disable the "Windows GPU" in OSX and the "Mac GPU" in Windows?

  3. thread starter macrumors 65816


    Jul 6, 2000
    I heard you can select the default GPU in Vista. The problem with having two GeForce 8800s, though is that the GTX requires two power inputs and the GT requires one. That's a total of three and the Mac Pro only has two power feeds.

    What two cards did you have in mind?
  4. macrumors 6502a

    Jun 7, 2006
    Dumbass question,that I propably know the answer allready..

    You cant split a feed from the psu and connect both ends of the split to a card?

    It is that one feed gives you certain amps/watts and thats it?

    Just that somebody mentioned that you can use a 8-to-6 pin adapter if your psu only happens to have a 8pin power free to power a 6 pin card if neccessary..
    Uumkay...I´ll shuddup.
  5. macrumors 6502

    Jan 6, 2008
    I made a thread (might be on pg 2 of this forum) about Crysis running pretty well with the ati 2600. If you plan to test this game, I'd like to know your results.
  6. macrumors 68020

    Mike Teezie

    Nov 20, 2002
    What is the installation process for these video cards? You don't just plug it into the slot and go?

    I have an 8800GT on order to replace my 2600. I thought it would be just plug and play.

    Excuse my ignorance.....:eek:
  7. thread starter macrumors 65816


    Jul 6, 2000
    The Mac version of the GeForce 8800 GT is plug and play for Mac OS X. You'll need the correct drivers for Vista booting up on a Boot Camp partition.

    In our case, we're waiting for our Mac version of the GeForce 8800 GT kit to arrive (sometime in early March). So since we had a PC version of the GeForce 8800 GTX "laying around," we decided to install it and see if the Vista partition could boot it. And it did.

    We just finished benchmarking Prey at 1920x1200 "High Quality." We get 155 frames per second. Compare that the a Radeon X1900 XT under Mac OS X on the same 3.2GHz Mac Pro. It attains only 64 frames per second.

    It's just an experiment to show the potential if Apple were to offer a high end version of the GeForce 8800 series.
  8. macrumors 68020

    Mike Teezie

    Nov 20, 2002
    Excellent. Thanks for the reply!

    All this kind of talk made me wonder if there were more power leads or something I was going ot have to hook up:

    Glad it's easy to do for a video card rookie like me.
  9. thread starter macrumors 65816


    Jul 6, 2000
    There is a 300 watt limit to what you can put on the PCIe bus. The GeForce 8800 GTX needs two power feeds because it uses at least 178 watts.

    Even if I could find a 6 pin to 6 pin splitter (which I doubt exists), I don't think the PCIe bus can handle anything other than a Radeon HD 2600 XT -- which doesn't require a power feed and only uses 50 watts.
  10. macrumors newbie

    Jan 10, 2008

    Are you getting the 8800GT upgrade kit? If so, do you plan on trying it out in the older Mac Pro's?

    Thanks in advance,

  11. thread starter macrumors 65816


    Jul 6, 2000
    I wanted to mention that the max wattage of the 8800 GT is 110. As for the 8800 GTX, the 178 watt rating is extrapolated from the fact that a stock GTX draws 165 watts and our sample is overclocked to match the core frequencies of the Quadro FX 5600 (which uses the same chip set and is rated at 178 watts -- and also uses two PCIe power leads).

    But that's good news. Someone on the Apple Discussions wanted to know if they could install both a GeForce 8800 GT and GeForce 8800 GTX in their Mac Pro "2008" (one for OS X, one for Vista 64). The answer is "YES," since the total wattage the two cards draw is 288 -- which is under the 300 watt limit for the PCIe bus.

    However, you will need to find a third power source for the GeForce 8800 GT since the GTX uses up the two PCIe power connectors on the motherboard. The solution is to get a generic PCIe power cord (4 pin molex on one end, 6 pin PCIe on the other) from Xconnect and plug it into the power lead in the lower, unused optical drive bay.
  12. Guest

    Jan 28, 2008
    So how does G92-core 8800GT compare against G80-core 8800GTX? In what instances will the 8800GT outperform the 8800GTX?
  13. thread starter macrumors 65816


    Jul 6, 2000
    Anandtech explains how the G92 is derived from the G80:

    And the same article has benchmarks showing that the stock clocked GTX is always faster than a stock clocked GT, but not by much:

    Our GTX is overclocked to compete with the Quadro FX 5600 so it's not necessarily a fair comparison to the stock clocked GeForce 8800 GT.

    Bottomline is that the 8800 GT uses much less power than the GTX and is only slightly slower than a stock clocked GTX. Apple made the right choice in terms of cost vs speed and power draw vs speed.
  14. macrumors regular


    Aug 25, 2006
    Perfidious Albion
    Two cards?

    So If what I'm reading is right, then you get a Mac Pro with the stock 2600 card and use that for most things, and also have in the machine a GeForce 8800 GTX that comes into play when you wish to do a bit of windows gaming?

    But is the 8800 really that much slower than the GTX?

    I'm itching to buy a Mac Pro to replace my aged games PC and me little Mac Mini, this could be the way forward?
  15. macrumors 6502a

    Nov 10, 2006
    Nice rig! I am waiting to see if any enterprising hacker can extract the firmware from a Mac 8800 and flash it on to a PC 8800.
  16. macrumors 6502

    Jan 6, 2008
    How do you get to this power lead, by removing the HDD in bay 1?
    Also, is that safe? Is it meant to handle up to a 110W component?

    Also, where are the aux connectors located on the Mac Pro?

  17. macrumors 65816

    Jan 9, 2008
    Your best bet for speed is actually to use four Voodoo5 6000s in quad SLI. Little known fact.
  18. thread starter macrumors 65816


    Jul 6, 2000
    You pull the optical bay assembly out. It pops right out. Once you plug into it, you run the power lead down the front next to the front grill and into the PCIe bay.

    Good question on the power output. I don't know how much wattage it can handle. I guess I need to do research on that.

    As for aux power connectors, the only ones other than the unused power lead in the lower optical bay are the two 6 pin plugs on the motherboard in the PCIe bay.
  19. thread starter macrumors 65816


    Jul 6, 2000
    You read it right.

    The 8800 GT isn't that much slower than a normally clocked GTX but my sample is overclocked. It's only an experiment by "the mad scientist." I intend to replace the Radeon HD 2600 XT with a GeForce 8800 GT kit I ordered.

    As for flashing the 8800 GTX with Mac ROM code, I understand that the chipset is the same as the Quadro FX 5600. I'm told that the 8800 GT code won't work. You would need to flash the GTX with the Quadro code if you want a "killer" GPU for gaming on both Mac and PC.
  20. macrumors 6502

    Jun 18, 2007
    Flashing to Quadro would probably impede it's gaming performance, as Quadro is not meant for gaming at all.

    As for 8800GTX vs. 8800GT... well the 8800GT is G92 core which is basically a revision of the G80 core of the 8800GTX. The GTX was almost a year old when the 8800GT arrived, so the fact that the 8800GT draws less power and performs about the same (for half the price no less) makes it quite an amazing card. That said, I can't wait for the 9 series to come out...
  21. macrumors 68040


    May 30, 2006
    I'm sorry but I thought this was pretty well-known. You can run any card you like in Windows but not in Mac OS X.
  22. thread starter macrumors 65816


    Jul 6, 2000
    Prey results for GeForce 8800 GT vs others

    I have some interesting Prey benchmark results.

    Prey at 1920x1200 "High Quality" -- all done with a Mac Pro 3.2GHz
    Radeon HD 2600 XT = 36 fps
    Radeon X1900 XT = 64 fps
    GeForce 8800 GT = 91 fps
    GeForce 8800 GTX = 155 fps *

    (* Vista 64 in Boot Camp partition; all others are Mac OS X Leopard)

    More to come...
  23. DWS
    macrumors member

    Feb 7, 2008
    Gee that GTX certainly bumps up the fps. Would be interesting to see the GT under Vista 64.
  24. macrumors 6502a

    Nov 10, 2006
    Did "Leopard Graphics Update" make any difference?
  25. macrumors 65816


    Jun 17, 2007
    You have a lot of memory (16 GB) in your computer.
    Does that help to play games?

    I have added a chart to show your above stats.
    It is taken from your home pag and revised to show the 8800 GTX.


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