770 GTX Classified Issues

Discussion in 'Mac Pro' started by Rgvega, Mar 5, 2015.

  1. Rgvega macrumors newbie

    Mar 5, 2015
    Hey all, this is my first post here and I have searched for my problem but not found anything.

    I installed an EVGA 770 GTX 4GB Classified in my 2009 Mac Pro (hacked to 5,1) and unfortunately it just clicks and nothing happens. I tried every combination of 6 pin to 8 pin adapter I could think of. I put my old GT120 back in to see that everything ran and it did. So the PSU isn't shot or anything. But as soon as I install the 770 back in, it just clicks and does nothing.

    It is a non-Mac rom PC version. But it should still work shouldn't it? Could my mini 6 pin power cables be defective?

    I am about to pop the card into a PC this week to make sure the card actually works (got it open box from EBay). But I was hoping someone had a similar experience to mine and could help me out.

    Could the Classified OC internal clock be too much for my Mac? Do I need to send it to MacVidCard so they can modify the clock speed to have a lower power draw?

    Any help would be awesome.
  2. Synchro3 macrumors 68000


    Jan 12, 2014
  3. flowrider macrumors 603


    Nov 23, 2012
    I'm running a MVC Modified GTX780 (Gigabyte 3 fan overlocked model). MVC modified the 8 pin connectors by shorting out a couple of the pins. The power draw has not been changed. The card's about a year old now and works fine in my 5,1 Mac Pro.

  4. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Computers are an exact science.

    That phrase is full of wiggle room and doesn't specify anything.

    If you bought a toaster and didn't plug it completely in would you be surprised when it didn't work?

    If there are 2 @ 8 pins on the card, they aren't optional, or giving you a choice of which ones to populate.

    The dual 6 to 8 adapters that ship with most cards will only populate the sense pins if one side is plugged in but not the other. They are meant to have both sides plugged in. The single 6 to 8 adapters usually trigger the sense pins.

    If you want actual help you will need to include actual details.
  5. Rgvega thread starter macrumors newbie

    Mar 5, 2015
    Thanks for replying MacVidCards. What I meant by that sentence is that I have tried using two 6-8 pin adapters, and also the tried using the dual-6 to 8 pin adapter that comes with the card in conjunction with the regular 6-8 pin adapters. I've also tried plugging in the 6 pin cables into the 8 pin directly (I had heard some cards would accept a 6 pin into the 8 pin).

    So I just went through all of the possible combinations just to make sure.

    Today I'm going to pop it into my friend's PC to double check that the card actually works.

  6. Rgvega thread starter macrumors newbie

    Mar 5, 2015

    Since I'm waiting for my friends PC to become available later today, I decided to start trying to isolate the problem elsewhere.

    I think it may be my PSU or logic board or my mini-6 pin cables.

    I decided to pop in an old 8800 GTX I had lying around (Dual 6 pin). It still produced that click sound and no boot up. I don't think my PSU or logic board likes anything being powered by the 6 pin cables.

    Could it be I got bad cables? I got them from Amazon.

    Or do I have to worry about something more serious like my PSU or logic board? :/
  7. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Easy enough to trace the wires.

    They should connect same pins on big and little ends.

    Somewhere here I have a piece of criminally incompetent construction. It is a 6 to 8 adapter that crosses polarity. Shorts the computer right out, sort of what you are describing.

    Once this happens do you have to do an SMC reset to do the next boot?
  8. Rgvega thread starter macrumors newbie

    Mar 5, 2015
    Yup! That's exactly what I have to do. So do you think it's just two bad 6 to 8 pin adapters?
  9. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    If you aren't using them to power the 8800GTX then they can't be the problem.
  10. Rgvega thread starter macrumors newbie

    Mar 5, 2015
    I'm going to try Sata to 6 pin adapters in conjunction with the 6 pin to 8 pin adapters. Maybe my mini PCI express 6 pin ports are shorting out the Mac.
  11. Rgvega thread starter macrumors newbie

    Mar 5, 2015

    So I got my SATA to 6 Pin cables today and I finally got the card working. Yay!

    I connected one of the cables to a free SATA connection and the other one to one of the mini 6 pin connections. I think my computer doesn't like both mini-6 pin connectors being used at the same time. There might be a short somewhere. Right now I'm using mini PCI-E Aux A and its working fine. There must be a short with Aux B.

    This will be a good enough solution for me especially when I'm able to successfully route the extra SATA connection from my disk drive bay.

    (Anybody have any suggestions for routing a cable from the drive bay?)

    So if this happens to anyone, don't immediately assume it's the PSU. It could be a random short circuit in your logic board like mine.

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10 March 5, 2015