Resolved MAC PRO 4,1 and 5,1 PCIe AUX Power

Discussion in 'Mac Pro' started by syops, Mar 4, 2017.

  1. syops, Mar 4, 2017
    Last edited: Mar 7, 2017

    syops macrumors newbie

    syops

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    #1
    The Mac Pro 4,1 & 5,1 have plenty of PCIe AUX power, unless you need more than 300 watts for your GPU(s). Remember you get 75 watts from the PCIe slot. Each PCIe AUX 6 pin connector in the Mac Pro towers delivers 150 watts. Yes all three power pins in both of the PCIe AUX plugs are connected. The PCIe specifications don't required pin number two to have power, but it also does not prohibit it either. In the MAC Pro 4,1 / 5,1 it is connected. To be clear, this delivers the same power as a 8 pin connector without the extra sense and grounding pin on the 8 pin plug. Just buy the correct 6 to 8 Pin PCIe AUX cables and you are all set. I'm running a NVIDIA STRIX 980 Ti OC with two 8 pin plugs (150w + 150w + 75w = 375w). The Mac Pro 900+ watt power supply can handle it. I also have two 130 watt x5690s. No issues during stress testing. Need more power... Cut the plug off the apple power supply and terminate it with the standard ATX connectors.. Then you can run additional power from a new replacement power supply of your choice.

    Make an intelligent choice. If you use something more, it should wear out sooner. Some of these machines are 7 years old and taxing a 7 year old power supply can cause it to reset or become inoperative.

    Here is some great information about computer power and how much you can use.

    http://www.overclock.net/a/gpu-and-cpu-power-connections
     
  2. h9826790 macrumors 604

    h9826790

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    #2
    375W is just the config that that hardware can handle, not it will pull that much. The NVIDIA STRIX 980 Ti OC can hardly draw 275W even under high stress (Furmark).

    In reality, your card may be drawing 70W from the slot, and just around 100W from each mini 6pin, no where near 150W on any mini 6pin.
     
  3. syops, Mar 4, 2017
    Last edited: Mar 4, 2017

    syops thread starter macrumors newbie

    syops

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    #3
    If the STRIX 980 Ti OC can hardly pull 275 watts, why would the manufacture put a more expensive 8 pin connectors on? Why not a 6 and a 8 pin like the newer lower power Pascal cards? I think it is for the folks that really like to overclock their equipment. So this is why ASUS put the bigger power plugs on the card.

    As for how much power can be drawn from the 6 pin connector on the Mac Pro 4,1 | 5,1 , it makes sense the power protection will shut the machine down when the power supply limit is exceeded. The Mac Pro 4,1 | 5,1 has a 980 watt power supply. So if we where to use 375 watts just for the GPU, there would be 605 watts for the system. In my case I have two x5690s, If the CPUs used the max wattage there would be 345 watts left to run everything else. I think there is still enough margin on the power supply.

    The pin out of the mini 6 pin PCIe AUX on the MAC PRO 4,1 | 5,1. looking at the pin diagram, you can see the only pins that provide power on both the 6 and 8 pin PCIe AUX are pins 1,2 and 3. On the 6 pin plug, pin number 2 may or may not be connected. See note in diagram.
    ac82eb1d_pinout.png Unknown.jpeg

    Yes the number 2 pin is connected on the MAC PRO 4,1 and 5,1. Electrically by jumping the extra ground and sense as depicted in the picture you signal the GPU it is a 8 pin connector. If there are only two power pins in this configuration you may run into a overload issue, but the Mac Pro has all three pins powered. Yes you can draw the maximum 375 watts for a single GPU on the MAC PRO 4,1 | 5,1.

    Here are the meter tests showing all three power pins connected with power.

    PIN 1.JPG.jpeg PIN 2.jpeg PIN 3.JPG.jpeg

    Bit-Tech did a review on the Strix 980 Ti OC. Looks like the GPU is using well over 300 watts.

    Screen Shot 2017-03-04 at 17.48.12.png

    https://www.bit-tech.net/hardware/graphics/2015/08/07/asus-geforce-gtx-980-ti-strix-review/10
     
  4. Grumply macrumors newbie

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    #4
    Really? Are you certain that both mini 6-pin ports can deliver 150w each? All of my reading on the subject suggested they were limited to 75w each.
     
  5. thornslack macrumors regular

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    #5
    The article notes the power draw is for the entire system, not just the GPU.
     
  6. syops, Mar 4, 2017
    Last edited: Mar 4, 2017

    syops thread starter macrumors newbie

    syops

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    #6
    Yes it shows the system at idle and at GPU load, the difference is 337 watts. I going to say the majority of that is the GPU. So I said the GPU is using more than 300 watts.
     
  7. pastrychef macrumors 601

    pastrychef

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    #7
    Yup, 6 pin provides 75W. 8 pin provides 150W.
     
  8. syops thread starter macrumors newbie

    syops

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    #8
    Yes.

    The Mac Pro 4,1 | 5,1 will provide 150 watts for each 6 pin plug. Why? The 8 pin plug has 3 - 12 volt pins and provides 150 watts. The 6 pin plug is specified to only have 2 - 12 volt pins and provides 75 watts. But many manufactures deliver 12 volts on all 3 pins on the 6 pin plug. So why is there an 8 pin plug if 6 pin plugs can give you 150 watts. Because not all 6 pin PCIe AUX plugs have all three power pins connected. But in the case of the MAC PRO 4,1 | 5,1 all 3 pins are connected, the same 3 pins on the 8 plug. 8 pin plugs are only around to ensure pin number 2 is also powered. It is my understanding many manufactures connect pin number 2 in the 6 pin plug, but it is not guaranteed. So thats why we have 8 pin plugs.
    --- Post Merged, Mar 4, 2017 ---
    Again this is on the MAC PRO 4,1 | 5,1. All three power pins are connected, the same three pin on the 8 pin plug. So yes you will have 150 watts from this motherboard. You just need the correct 6 to 8 pin plug. In the picture you can see the additional pins are just jumpers.
    Unknown.jpeg
     
  9. pastrychef macrumors 601

    pastrychef

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    #9
    The problem is not the spec or whether pin 2 is providing power. The problem is the traces on the motherboard. They were not designed for 150W. It's like trying to use wires as thick as dental floss to make an extension cord for your air conditioner or refrigerator.
     
  10. h9826790, Mar 4, 2017
    Last edited: Mar 5, 2017

    h9826790 macrumors 604

    h9826790

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    #10
    I am totally open minded to your theory. And I want that's the truth indeed (I am sure get the correct cable is much much easier / safer than the Pixels mod). However, your post didn't shows that any mini 6pin was delivering 150W, nor your 980Ti was pulling way over 300W from the cMP. That 337W difference in that graph is the ENTIRE system, including more demand on RAM, CPU, etc. Unigine Valley is not (and cannot) only stress the GPU but leave everything idle. And don't underestimate the power consumption on the CPU, there is a big difference between true idle and only 1 thread is being used. Especailly that 5960X (140W TDP) was OCed to 4.2GHz and over volt to 1.25V.

    https://www.bit-tech.net/hardware/graphics/2015/08/07/asus-geforce-gtx-980-ti-strix-review/2

    The CPU can easily pull way more than you believe. I personally believe the following review is a more appropriate one when calculating the 980Ti's power consumption.

    https://www.techpowerup.com/reviews/ASUS/GTX_980_Ti_STRIX_Gaming/28.html

    I totally understand that you showed us that there are 3 pins connected. However, so far, all experience shows that once the demand over 120W on any mini 6pin, the cMP can shut itself down anytime. We are not talking about "in theory" but the real world. I also understand that a "correct cable" is required. However, quite a few users here did try the mini 6pin -> 8pin, seems none of them so far can really draw 150W from only one mini 6pin. I doubt if no one get a "correct cable" so far.

    I know I should not ask you to further OC / over volt your 980Ti and then run Furmark to try the max possible power draw on your system. And I don't want to risk your system as well. However, it seems that you are the only person that have the 100% correct cable on hand and able to run the test properly. If you unable to show us the definitive prove, it's really hard to judge if your theory really work on the cMP.

    Once again, I am open minded to your theory. I did study both the Mac Pro 5,1 manual and the corresponding technician guide again, but unable to find any info about the limit of the 6pin. However, until anyone provide a reliable proof, I will still treat the real world limit of those mini 6pins are ~120W. That's the best we can do so far with lots of users experience. I wish you can successfully push this limit further, and tell us that all we need is just a correct cable.
     
  11. pastrychef, Mar 4, 2017
    Last edited: Mar 4, 2017

    pastrychef macrumors 601

    pastrychef

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    #11
    According to your theory:

    If a 6 pin connector only has pins 1 and 3 powered, it will provide 75W.
    If a 6 pin connector has pins 1, 2, and 3 powered, it will provide 150W.

    If you look at a PCI-e slot, it has 5 +12V lines (A2, A3, B1, B2, B3). Does that mean a PCI-e slot can provide 225W?

    What's missing is amperage in all of this.

    7w3QA.png
     
  12. syops thread starter macrumors newbie

    syops

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    #12
    Why would Apple put 12 volts on pin 2 if it can't support the load? That would only set the system up for failure. Better to not connect pin 2 at all per spec.

    As for the PCIe slot, the service manual says 300 watts is the maximum for all four slots total. I'm sure they mean 75 watts per slot. Hmm that is a good question. Can one of the PCIe slots use more than 75 watts? I just don't think the cards are setup to draw more than 75 watts. I'll see what I can find out about that.
     
  13. pastrychef macrumors 601

    pastrychef

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    #13
    No one other than Apple can tell you why pin 2 is live. But they didn't make those 8 pin headers. They are 6 pin headers. They also put in safeguards that shut down the computer when load becomes too high.

    You have not factored in amperage in to your theory. You are welcome to try and power a 225W card using a single motherboard header to see what happens and run Furmark overnight.
     
  14. mattspace macrumors 6502a

    mattspace

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    #14
    putting 8 pins worth of power into a 6 pin connector, does sound like a very Apple thing to do if they wanted to be able to show "mac edition" video cards as being superior to "equivalent" compatible 6 pin PC cards, back when they did bakeoff type comparisons.
     
  15. h9826790 macrumors 604

    h9826790

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    #15
    It CAN support the load, because it's a 6 pin design! Anything more than 75W means it can support the load, including pin 2 is connected. You are the person to interpret that pin 2 connected = 150W avail, not Apple. And Apple never tell anyone to use that pin's power, never say that their mini 6pin rated for more than 75W. They didn't setup anything for failure but just make a very capable 6 pin power source (which practically can deliver up to ~120 from the test so far, but still consider limit at 75W).

    BTW, looking forward for the 1st user report that able to run Furmark on a FuryX with just the mini 6pin's power. For power drawing test, still nothing can beat the AMD card :D
     
  16. syops, Mar 5, 2017
    Last edited: Mar 6, 2017

    syops thread starter macrumors newbie

    syops

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    #16
    3DMARK TIMESPY complete. 130% GPU overclock..
    MAC PRO 2009 | ASUS STRIXS GTX 980 Ti OC | Windows 10 Pro

    I'm on the road, had to remote in to run the test over the cell hotspot.

    Screen shots.

    Screen Shot 2017-03-05 at 14.29.41.png

    Screen Shot 2017-03-05 at 14.30.27.png

    Screen Shot 2017-03-05 at 14.30.39.png

    Screen Shot 2017-03-05 at 14.31.11.png

    Screen Shot 2017-03-05 at 14.31.20.png

    Screen Shot 2017-03-05 at 14.31.29.png

    Screen Shot 2017-03-05 at 14.31.44.png

    Screen Shot 2017-03-05 at 14.32.04.png
    --- Post Merged, Mar 5, 2017 ---
    3DMARK TIMESPY complete. 130% GPU overclock..
    MAC PRO 2009 | ASUS STRIXS GTX 980 Ti OC | Windows 10 Pro

    I'm on the road, had to remote in to run the test over the cell hotspot.

    VIDEO ;0



    No problems with the overclock. ;-)

    Hmm.. looks like someone flagged my video of the MacPro running the 3DMARK as inappropriate. I'll try to get the video back up.

    :) video is back up.
     

    Attached Files:

  17. h9826790 macrumors 604

    h9826790

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    #17
    Stable 30% OC with that high stock clock speed, a very nice card (you made me really want this card now, haha). I tried to read those chart, but not very clear, and couldn't find the power draw. I understand that there is no way to tell the 6pins power consumption in Windows, but just the card's total power draw. However, I can't quite get it from the screenshot.

    I can see the total power max at 114%, but what's the base power consumption? I don't think the software base on 375W and draw further 14%.

    Anyway, thanks for helping us to find out the real limit more precisely. Please no rush, we can figure it out after you back home and run more tests. In any case, please don't risk your machine.
     
  18. thornslack macrumors regular

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    #18
    I find this hard to believe. My Titan X superclocked will shut down my cMP if I over clock it at all running off a standard mini six pin and a mini six to eight pin.
     
  19. h9826790, Mar 5, 2017
    Last edited: Mar 5, 2017

    h9826790 macrumors 604

    h9826790

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    #19
    IMO, 6+8 is the problem, 8+8 is actually better. Because it's not about the total power consumption, but can the user balance the load between the mini 6pins.

    For 6+8 pin card, you TitanX will heavily rely on the 8 pin, therefore, draw way too much on one of the mini 6pin, that will trigger the shut down protection.

    e.g. Your card can only draw 75 form slot, 75 from 6pin A, 120W from 6Pin B. Which is only 270W max. In fact, I don't think the manufacture will decide a power consumption that so "optimised" for cMP. 100% on slot, 100% on 6pin, but 80% "only" on the 8pin. If we assume there is a 5W build in buffer for the slot / 6pin and 10W buffer for the 8pin. Your card will be designed to draw up to 70+70+140 = 280W max, which is enough for the TitanX, even for minor OC. However, In cMP's case, we can only get 70+70+120 = 260W practically, anything above that may shut down the Mac. So, there is almost no room for your card to OC by considering it can pull 250W already.

    In OP's case, a 8+8 card can practically draw 75+120+120, which is 315W. Even we assume the same 5W and 10W build in buffer apply. The card can still draw up to 300W before it shutdown the Mac. Because there is no point for the card to heavily rely on one 8pin only, so, highly likely the manufacture will balance the load between them, and coincidentally make it a more cMP friendly card.

    And this is why I want OP can prove that either mini 6pin can actual deliver 150W without trigger the shutdown protection (IMO, for this test, anything >140W is good enough). Because his card may naturally balanced the load, which make him so much easier to OC the card, and still just stay below the shutdown limit.
     
  20. Grumply macrumors newbie

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    #20
    It still seems to me, that the safest option (for internally powering a big gpu) is to use a combiner cable to feed 150w from both mini 6 pins into a single 8-pin cable, then use an adapter to send power to the 6-pin port from one of the internal SATA connections (which I was told is capable of supplying up to 54w).

    This would give you:
    - 75w from PCIe port
    - 150w from dual mini 6-pins
    - 54w from SATA connection

    For a total of 279w, which should cover a Titan X (which is the beefiest thing you can currently put into a cMP).

    *Someone please correct me, if I've got those numbers wrong.
     
  21. syops, Mar 5, 2017
    Last edited: Mar 5, 2017

    syops thread starter macrumors newbie

    syops

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    #21
    --- Post Merged, Mar 5, 2017 ---

    I agree. Use 8 and 8. Look at the power consumption data of the 980 Ti OC and the Titan I just posted. They are very similar, but the 980 Ti OC uses more power. If my 980 Ti OC works with a 30% overclock, I would think your Titian will work. Also the GPU just might not be able to handle the superclock setting you have. Some chips are better than others. Just something to consider.

    IMG_6802.PNG

    IMG_6803.PNG
     
  22. thornslack macrumors regular

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    #22
    The issue is the power draw not the OC. But the thread raises an interesting point which I had initially missed. Sadly the TX uses a 6- and an 8-pin so I have no means of easily replicating your scenario.
     
  23. pastrychef macrumors 601

    pastrychef

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    #23
    Use iStat Menus to get a reading of how many amps the aux power connectors are pulling. This will let you know how many watts are being pulled from each connector.
    394144-3aed399a485fe1c8d05b296120ee1174.jpg.png
     
  24. h9826790 macrumors 604

    h9826790

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    #24
    That reading is maxed at 8A (96W), not accurate for high loading.
     
  25. pastrychef macrumors 601

    pastrychef

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    #25
    In my experience, the readings were quite accurate. It ramped up and down with GPU load.
     

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