GTX 690 in MacPro4,1 with no external PSU

Discussion in 'Mac Pro' started by 5050, Apr 27, 2013.

  1. 5050 macrumors regular

    May 28, 2009
    Hi guys,

    Looking for some advise on using a GTX 690 in a MacPro4,1 without an external PSU (Tutor if you're reading this, I would definitely be interested in your opinion).

    To preface, I'm thoroughly up to date on the subject here on the MacRumors threads as well as countless other forums which advocate the use of an external PSU with the GTX 690 in a Mac Pro. In fact, I ordered the 660W PSU below:

    This PSU however arrived DOA.

    After installing the GTX 690 into my MacPro4,1 and with a breath of anticipation I flipped the power switch to the on position. To my disappointment, no spinning fan and the PSU "whisper quiet." I first assumed that maybe it was running "fanless" and "quieter" than advertised. No dice. This PSU is now en route back to Newegg for exchange.

    So now my MacPro4,1 is sitting here with the GTX 690 installed in slot 1 of the PCIe 2.0 with no external PSU.

    So my questions are:

    1) If I gut/strip everything out of my MacPro4,1 (see list below) can I use the GTX 690 using only the internal MacPro4,1 PCIe power (via 6+2 pin adaptors) -- i.e. without an external PSU -- in order to simply "test" the card and see if it is capable of booting into OS X?

    • The power from the optical drive DVD
    • 2 out of the 4 available SATA II bays (only 2 will be occupied for OS X installed across two Samsung 840 Pro 256GB drives in RAID 0 configuration)
    • The only PCI device installed will be the GTX 690
    • And any other items that I'm forgetting (please advise) . . .

    I don't want to chance any damage to the GTX 690 or my system, but I figure if I unload all the items above from drawing power from the total allocated power in the MacPro4,1 this might have a chance of working with minimal to no risk.

    You can see the specs on my MacPro4,1 here, which notes that the MacPro4,1 has a "300W combined maximum for all PCI Express slots."

    And here is the GeForce GTX 690 specification page for reference:

    2) What is the minimum OS X requirement to run the GTX 690? I have seen a broad range of users reporting success with everything from Snow Leopard to the latest 10.8.3 release of Mountain Lion.

    3) I've installed the Mac CUDA 5.0.45 driver for MAC from the NVIDIA website. Anything else I need to download and install to get the GTX 690 running on my MacPro4,1?

    Many thanks in advance!

  2. lewdvig, Apr 27, 2013
    Last edited: Apr 27, 2013

    lewdvig macrumors 65816


    Jan 1, 2002
    South Pole
    This sort of thing happens all the time when PC upgraders stick a card in their HP or Dell that is too powerful for their stock PSU.

    To run that card, you would need a capable PSU with 12v rail with sufficient amperage.

    A MP PSU is awesome, but usually lacks enough amperage on the 12v rail for a card like that.


    Your GTX 690 needs a single 12v rail with 38a. The stock PSU is not going to cut it.

    Best case scenario IMO, you get a barely stable machine. Worst case you damage some components or get flaky writes to your HDD or memory which could lead to having to reinstall the OS and potential file loss.

    I would be patient and get the right PSU.
  3. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    Did you short the "power on" pins on the PSU?

    PC style power supplies don't "sense" when to turn on, they are switched on externally. This is IN ADDITION TO turning the switch on.

    There is a green and black wire on every single PC power supply that needs to be connected if you wish to use it without a motherboard to turn it on.

    Very often forgotten or overlooked by Mac types who don't usually build PCs.

    Try this, type "short green and black" into Google.
  4. Tesselator macrumors 601


    Jan 9, 2008
    ^^ What MVC says! Yes.

    But I just wanted to add that you could probably install the card without the aux PSU - even without disconnecting everything else. The card idles low enough.

    The problem is that as soon and the card requests more power you begin over-drawing current that the PSU, traces, and wires weren't rated to supply.

    MP is a pretty robust and intelligent design. At first and probably for months and months, all you will likely see is lots of system instability. KR's, system resets, sudden power downs, and so on. But the stress will eventually break something - likely the $280 PSU but also maybe the $350 motherboard. And although probably rare and unlikely, it could also immediately break something too.
  5. 5050 thread starter macrumors regular

    May 28, 2009
    Thanks for your reply.

    Yes, I turned on the PSU first before firing up the Mac Pro.

    The 690 was seated in the PCIe slot (so connected to the motherboard). Either way, I expect flipping the power switched on the PSU before turning on the Mac Pro's should have powered the 690, even with the computer's power off.

    Not sure what you mean by shorting the PSU. There wasn't any green and black wires included with the PSU to use. Only connected the power supply cable and the two 6+2 pin cables to the 690.
  6. 5050 thread starter macrumors regular

    May 28, 2009
    Is the PSU in the Newegg link I included above enough to sufficiently power the 690?
  7. 5050, Apr 28, 2013
    Last edited: Apr 28, 2013

    5050 thread starter macrumors regular

    May 28, 2009
    Ahhh, I think I understand now. So if you're using a supplementary external PSU to power a device like the GTX 690 in a Mac Pro, and that PSU isn't somehow connected to the motherboard of the Mac Pro, the PSU will not power up?

    If so, what function is the motherboard actually doing to make the PSU (internal or external) fire up?

    My question then is how do external devices like USB/FireWire HDDs and DVD/Blu-Ray players capable of powering up when connected? Are they "internally" shorting the power that is mentioned in your link above?

    More importantly, is it possible to use a SPLITTER of sorts (like a cable TV or telephone splitter) in order to establish sync between the MacPro4,1's powering up/down and sleep/wake cycles?

    Also, any ideas on minimum OS X to run the 690?

  8. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA

    Please find a moment to read what I wrote and click on the link. I don't think you are understanding.

    You bought a PC Power Supply. It has to be treated as if it is in a PC.


    Google is really useful. Copy and Paste as I mentioned. First result explains it.
  9. Tesselator macrumors 601


    Jan 9, 2008
    Yup, and there are a number of youtube videos showing it too if the terminology is messing with ya...

  10. 5050 thread starter macrumors regular

    May 28, 2009
    Hi MVC, thanks again for your original reply. Please see my response to 666sheep above. Would appreciate your thoughts.
  11. 5050 thread starter macrumors regular

    May 28, 2009
    Seasonic USA Platinum Series 660W (SS-660XP2)

    Hi lewdvig,

    Thanks for your reply. The PSU I purchased is the Seasonic USA 660W in the link below.

    I've attached the specifications for this PSU directly below. I don't see any product details (i.e. to my novice eye) that specify whether this is a single +12V rail or multi +12V rail design. How would I determine this?

    Also, more importantly, would this PSU qualify for the GTX 690 (i.e. single +12V rail with 38A as you noted in your previous reply)?


    Many thanks!
  12. GP-SE macrumors 6502

    Feb 27, 2013
    the PSU you bought is an excellent PSU, SeaSonic makes some of the best PSU's! Also it has enough power, you just need to google how to short the pins on the PSU to power it on.
  13. 5050 thread starter macrumors regular

    May 28, 2009
    Thanks much for this Tesselator, this really helps.

    Trying to do a little research now to see if there's an alternative to the paper clip option, like an adaptor or a 1-pin cable that would accomplish the same without jerry-rigging a paper clip. If I find any viable options, I'll post here.

    Thanks again!


    Thanks GP-SE. I'm new to all this.

    Do you know how I can confirm if this PSU is a single or multi +12V rail design (it might detailed in the specifications image I attached above, but it's all Greek/Chinese to me)?
  14. 5050 thread starter macrumors regular

    May 28, 2009
    Dual PSU 24-Pin Adapter Cable

    Can either of these adaptors be used to "jump two PSUs" using "one" MacPro4,1 motherboard?

    Also, where would I locate the 24-pin Connector on the MacPro4,1? Had a look inside the case and can't seem to locate it . . .
  15. Dr. Stealth macrumors 6502a

    Dr. Stealth

    Sep 14, 2004
    SoCal-Surf City USA
    The function the motherboard performs is this... The little round power button on the front of your Mac is connected to the motherboard. When you press the button you "Short" the power supply leads that instruct it to turn on.
  16. GP-SE macrumors 6502

    Feb 27, 2013
    it is single +12V rail, so very good!
  17. El Awesome macrumors 6502

    El Awesome

    Jul 21, 2012
  18. 5050 thread starter macrumors regular

    May 28, 2009
    Thanks much! Where did you find this information (sorry again if I'm a bit dull when it comes to interpreting this information in the spec sheet)?
  19. GP-SE macrumors 6502

    Feb 27, 2013
    from the spec sheet (+12v)
  20. 5050 thread starter macrumors regular

    May 28, 2009
    So the spec sheet lists 660W at 55A?

    Again please forgive my ignorance, but what about the other "Combined Loads" for "125W, 6W, and 15W" listed? Why are there multiple "DC Output Voltages" listed in the spec sheet?

    Thanks again.
  21. GP-SE macrumors 6502

    Feb 27, 2013
    to be honest I'm not sure why the +12v has all 660Watts, since the Power Supply is rated for 660watts TOTAL.
    However I wouldn't worry about it, it'll power a GTX 690 without issue, and it's from one of the best PSU makers in the industry.
  22. 5050, Apr 28, 2013
    Last edited: Apr 28, 2013

    5050 thread starter macrumors regular

    May 28, 2009
    Dear MacVidCards,

    I think that I might have found an ideal solution to run both the MacPro4,1 PCU and the external Seasonic 660W PSU together so that they are both "power aware." Check out the hardware list below:

    1) SATA to LP4 Power Cable Adapter - F/M

    2) Add2PSU Multiple Power Supply Adapter

    For the shortest and most direct path out of the MacPro4,1 enclosure, I plan to empty out the 4th SATA II HDD bay and connect the open "4th HDD bay SATA power/data connector" to the "SATA 15-pin male to IDE 4-pin female adaptor" which will connect to the IDE male on the "Add2PSU Multiple Power Supply Adapter," which will finally connect back to the "Seasonic 660W PSU" via the 24-pin power supply cable. The 24-pin power supply cable will snake out of the MacPro4,1 enclosure through a PCIe opening in the back of the computer.

    The key to making this all work is obviously the Add2PSU adapter. Read more about it here:

    With this setup, the Seasonic 660W PSU should be "power aware" when the computer is powered up or put to sleep along with the rest of the internal Mac Pro installed hardware, correct?


    Awesome, thanks again GP-SE! Just out of curiosity, if I scaled into another GTX 690, how many Watts, Amps should I look into in order to power both cards (with a little extra power for "headroom" as I've heard) from one PSU?
  23. xcodeSyn macrumors 6502a

    Nov 25, 2012
    Looks like the setup would sync the external PSU with the MP's PSU although it could be a mess to route the cables. Unless you have plans to use your external PSU to power two GTX 690's, what I don't understand is why didn't you choose the booster X5 like most others did? It is more compact and can be easily installed in the second ODD bay, and has a built-in molex plug to sync with the main PSU.
  24. GP-SE macrumors 6502

    Feb 27, 2013
    From a quick google search, it looks like the GTX 690 requires:
    38 Amps on the +12v Rail
    TDP: 300 Watts

    38amps x 12Volts = 460Watts, yet the card has a TDP of 300watts.

    If you go by Amperage you need a PSU that has 76 Amps on the +12v Rail (912 Watts on +12v Rail)

    If you go by Wattage\TDP you need a PSU with 600 Watts on the +12v Rail
    (50 Amps on the +12v Rail)

    Very Confusing

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