Orig. Mac Pro Quad now with 4870x2

Discussion in 'Mac Pro' started by wsgroves, Aug 21, 2008.

  1. wsgroves macrumors member

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    Sep 19, 2006
    #1
    Hi guys. You may remember I was one of the originals to put a 8800GTX in my mac pro under windows.

    I have recently upgraded my mac pro with a new Ati 4870x2 card.

    I wanted to post because some of you may want to do this for the pc side to game so lets get to my findings.

    First of all, I installed the card and hooked it up from the power cables coming off of the cd drives just like I did my nvidia 8800gtx.
    THIS DID NOT WORK FOR ME.
    The machine would turn on and chime but upon boot would shut off completely or go into a power down state.
    From what I can tell, the PSU will not handle the new 4870x2 card being powered by the lone cd rom power cable.

    Now, being I wanted to use this card while I build my gaming pc, I had a spare 500w BFG PSU lying around to test if indeed the mac pro PSU was the problem.
    I rigged the external PSU with a thick paper clip. Take one end and plug into the green pin on the MB connector and take the other one and plug it into a black pin. This powers the PSU without having it hooked to a computer.
    I now plugged it into the vid card and powered on the external PSU.
    Upon turning on the mac pro, viola....it booted and works perfect.

    I know. its not a good idea to run it like this but it does work.

    I wanted to let others know my findings with the original mac pro as I know alot of you use windows on it to game.

    I have the original Mac Pro 2.66 with 6gigs ram, 3 hd's, a blu ray burner and now the 4870x2 card.
    It plays really well for the betaish drivers on the video card. Oblivion plays at 2560x1600 with 12x effective Anti-Aliasing and 8x AF better then the 8800gtx did.

    Hope this info helps someone out.
     
  2. nanofrog macrumors G4

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  3. macz1 macrumors 6502

    macz1

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    #3
    Do you ever use OS X on your machine or it's configured Windows-only? It would be interesting to know what the GFX card does when booting OS X...
     
  4. wsgroves thread starter macrumors member

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    Sep 19, 2006
    #4
    Yea, its hot wired lol.

    No I have not tried osx. I figure its not even worth my time as I firmly believe it will not work. Here is a crappy pic with my cam phone.

    [​IMG]
     
  5. Pressure macrumors 68040

    Pressure

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    #5
    Did you really think that one standard molex connector would supply enough power? ;)

    There is only so much power which can be supplied over a single 12 volt cable.

    It can boot if you use the spare molex from the Superdrive bay and a 6-pin connector to the motherboard.
     
  6. AlexBlack macrumors newbie

    Joined:
    Aug 12, 2006
    #6
    This is awesome.

    Im not a PSU expert, but couldn't you have just plugged in the 2nd power supply to your powerstrip and then hooked it to your cards with 100% less hot-wiring?
     
  7. wsgroves thread starter macrumors member

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    Sep 19, 2006
    #7
    The extra psu wont turn on w/o the green and black pins in its motherboard connector tripped.
    Yea I wanted to try it with the superdrive cable and the motherboard power connector but I dont have one that connects to the motherboard.
    You have a website handy I could purchase one?
     
  8. nanofrog macrumors G4

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    May 6, 2008
    #8
    By chance, could you give a link or take a photo of the cable you first tried?

    It's a bit hard believing the PSU rated for 980W can't provide the power. IIRC, some like the 8 pin PCIe power cables use 2-4 pin molex connectors to supply the power.

    Just curious. :D
     
  9. Pressure macrumors 68040

    Pressure

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    #9
    You can purchase the cable direct from ATI here, only $12.99 to boot.
     
  10. Pressure macrumors 68040

    Pressure

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    #10
    It's quite simple. You cannot supply that much current through a single 12V cable. It's a switched-mode PSU, as every computer PSU is these days, and it converts 110 - 240 V AC power from the outlet, to several low-voltage DC power outputs (+/- 12V, +/- 5V and so on).

    Which is the reason why some graphic cards require more than one cable attached. In this case the Radeon HD 4870X2 needs one 6-pin PCI-Express connector and one 8-pin connector to get enough juice.
     
  11. nanofrog macrumors G4

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    #11
    I was under the assumption he realized that he needed both the 6 pin and 8 pin PCIe connectors to power the card properly. :eek:

    I wasn't sure what he'd done, or what he used.
    So I decided to try and keep it simple. Ask a question, get info, repeat. ;)
     
  12. Pressure macrumors 68040

    Pressure

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    #12
    I think he did know it needed both but his mistake were that he tried to power it through the same spare cable in the Superdrive bay :)
     
  13. nanofrog macrumors G4

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    #13
    Hmm...I think you're on to something here. :D
    Let's keep at him, and we'll get the details yet. :p
     
  14. wsgroves thread starter macrumors member

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    Sep 19, 2006
    #14
    I'll buy that cable and try to power it with the superdrive cable and the one off the sysboard.

    Yea I did know it needed 2 power connectors, a 6pin and 8 pin. I just figured I would try it off the cd power cables as my 8800GTX card which is a beast as well, worked fine off of those cables.
    The ati card came with a molex 6pin adapter and an 8pin adapter, its a Sapphire card. I have noticed not all the cards do come with the 8pin adapter.
     
  15. nanofrog macrumors G4

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    May 6, 2008
    #15
    Aha! Now you spill it. :D :p

    The 8800 is a baby compared to the HD 4870X2. Basically 2 graphics cards crammed on one PCB. :eek:

    Yeah, just get one of the 6 pin PCIe cables linked above, and there shouldn't be any problem. ;)

    Eliminates the FrankenPower PSU mess. :p
     
  16. macest macrumors member

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    Aug 22, 2008
    #16
    I have also installed the 4870x2 into my Mac Pro successfully. I used the 6-pin cable from my 8800GT and wired my spare molex connector from the optical bay to the included 8-pin adaptor. The downside at the moment is I'm stuck in Windows since my attempt to connect my 8800GT as well failed somewhat.

    I used the other molex to 6-pin cable (also included) to connect to the 3-way splitter I connected to get the 8-pin adaptor working (since it connects to 2 molex connectors vs. 1 with the 6-pin adaptor), but nothing appeared on screen using any of the DVI ports. I know it booted fine since I heard the Windows Vista chime that you get when the logo appears. I think it might be a driver conflict or something. Still investigating the issue.

    On a related note, anyone know of any UK retailers that sell the the PCI Express power cable that connects to the motherboard?
     
  17. nanofrog macrumors G4

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    May 6, 2008
    #17
    If I've understood your physical installation correctly, you need to use separate 12V power connector (4 pin flat molex) to attach the 6 pin PCIe cable.
    The cable you are searching for will do nicely as well. :D
    Saves a 4 pin power connector too. :eek:

    As far as locating the cable, I found a site here in the US that will ship to the UK. :) (Confirmed with a phone call) ;)
    http://www.svideo.com/x1900.html
     
  18. Pressure macrumors 68040

    Pressure

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    #18
    This is a Vista issue. It will only allow one graphic package to run at a time. So it's either nVIDIA or ATI I'm afraid.
     
  19. macest macrumors member

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    Aug 22, 2008
    #19
    Based on your response I subsequently removed the NVIDIA drivers and the Boot Camp display drivers. I managed to get it to boot with both cards, however it defaulted to the 8800GT to output the display (using standard VGA drivers) and refused to use the 4870x2. It also crashed a few times during boot. I then attempted to disable the 8800GT in the Device Manager to see if that would work, but it wasn't listed there. Any ideas?
     
  20. Pressure macrumors 68040

    Pressure

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    #20
    The problem with Vista is that it will only load one graphic package (driver) at a time.

    Unfortunately I don't have that much experience with Vista but try installing the Geforce 8800 GT drivers again with only that card installed. Then after installation disable it in the Device Manager and shut down.

    Then boot again with the Radeon HD 4870X2 inserted and proceed to install the supplied drivers. This might work.

    I have no way to test this but this is the only possible solution I can come up with.
     
  21. wsgroves thread starter macrumors member

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    Sep 19, 2006
    #21
    hmm ok interesting.

    I purchased one of the onboard 6pin pcie graphics cables that attach to the motherboard as listed above.

    I use it for the 6pin and an adapter for the 8 pin connected to the cdroms.


    The system would boot BUT upon initializing the display after login of vista, it would reboot every time. I plugin in the jury rig psu and it goes into windows just fine.

    It seems that the psu in the mac pro cannot handle the 4870x2 afterall =/

    I wasted money on the cable but hopefully this helps someone out.
     
  22. kabunaru Guest

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    Jan 28, 2008
    #22
    But can you max out Crysis with the 4870x2? That is the question.
     
  23. nanofrog macrumors G4

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    May 6, 2008
    #23
    Weird! :confused:

    The PSU is rated for 980W, so it should run the card. (Specs require 650W).
    What else are you running?
     
  24. wsgroves thread starter macrumors member

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    Sep 19, 2006
    #24
    Running a blu ray drive and superdrive, 3 hd's and 5 gigs of ram.

    No, you cannot max crysis settings out even with a 4870x2 at 2560 res.

    Maybe later i'll try to unplug all the hd's except the boot one and try just one cd rom.
     
  25. nanofrog macrumors G4

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    May 6, 2008
    #25
    I don't care about Crysis. :p

    It could be the short term power draw at start up is exceeding the PSU's ratings.
    By chance is there anything else, such as a second video card?

    BTW, do your HDD's support staggered spin up? (It could help).
     

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