Running a Mac Pro without a PCIE Fan and a HD 7970?

Discussion in 'Mac Pro' started by harkkam, Nov 8, 2012.

  1. harkkam macrumors newbie

    Nov 8, 2012
    I installed a new HD 7970 into my Mac pro 2010 and after boot it sends the PCIE fan into full throttle at 100% and becomes very loud.

    I'm running the 7970 in bootcamp to play some games.

    Do I really need the PCIE fan in the first place, the card is being kept pretty cool by the fans on the card itself.

    Will I do damage by running my mac pro without a PCIE fan in there?

    Also the card needs two eight pin connectors so what I did was simply take the 6 pin connector and get an adapter and turned it into an 8 pin adapter

    Is all of this stuff safe?
  2. ScottishCaptain macrumors 6502a

    Oct 4, 2008
    Yes, you need the PCI-e fan.

    The Mac Pro actively monitors the RPM of this fan. If there is no tach signal to monitor, then the system will likely shut down- so you won't be able to use it without that fan in place.

    Try resetting your PRAM and/or SMC (the former by holding CMD-OPT-P-R at startup, the latter by simply unplugging the machine and waiting a minute or two before plugging it back in). The PCI-e fan shouldn't be running at 100%, but then again, that's not a supported card so who knows what is going on there.

  3. DanielCoffey macrumors 65816


    Nov 15, 2010
    Edinburgh, UK
    And as for the 8-pin power lead to the 7970, NO it is NOT safe.

    According to reviews, the 7970 draws just over 300 watts at full load whereas the maximum the Mac Pro can supply is 225 so it is inevitable that you will cause serious damage your Mac Pro and sooner rather than later.

    You NEED to get a secondary power supply to feed the 8-pin connector on the 7970.

    I am surprised you spent all that money without doing some background reading first.

    It is not the rating of the Mac Pro PSU... it is the rating of the leads and traces in the logic board which WILL be damaged and soon too with that heavy power draw.

    Take the card out until you can get a secondary power supply to feed it from.
  4. Inconsequential macrumors 68000

    Sep 12, 2007
    No and no.

    You need to keep the fan there and you need an external PSU. Period.
  5. DanielCoffey macrumors 65816


    Nov 15, 2010
    Edinburgh, UK
    I think the answers to the questions are actually yes, yes and no.

    Yes you need the PCI-e fan. Yes you will damage it without that fan. No all that stuff is not safe.
  6. OrangeSVTguy macrumors 601


    Sep 16, 2007
    Northeastern Ohio
    Just buy a cheap PSU with 8 pin PCIe adapters. Use a paper clip to jump the green wire(only 1) to any of the black wires on the 20/24 pin motherboard connector. This will turn your external power supply on to feed power to your 7970. Don't disconnect any of the factory Mac Pro fans. You need them.
  7. slughead macrumors 68040


    Apr 28, 2004
    ^ This. There are a couple how-to's on this forum on low-cost ways to add power. I wrote one but am too lazy to search for it right now lol

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