1. #1

    7970 TDP / Power Draw

    So I just ordered one, and I'm curious about something before I go out and drop some money on a new PSU. Currently I have a multi-rail PSU with two 25a rails.

    Am I correct in assuming that the card will pull 75w~ from the PCI lane (pulling off the CPU/mobo rail)? I have no idea if modern boards still provide some of the required power to the GPU, google wasn't much help.

    If so, my 25a GPU rail (300w) should be plenty for this card, yes? Considering the highest power draw ratings that I can in reviews are around 270w (not total system draw). AMD is also no help with their advertised TDP ratings, seems as though every reputable reviewer has proven the cards easily raise above it.

    Thanks.
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  2. #2
    Love vague posts asking for help. Would be nice to let us know what PSU you actually have instead of just some numbers.

    Here.

  3. #3
    Quote Originally Posted by User007 View Post
    Love vague posts asking for help. Would be nice to let us know what PSU you actually have instead of just some numbers.

    Here.
    Vague? My PSU has two 25a rails. Pretty self explanatory. Also, as I have already stated, AMD's TDP numbers aren't accurate.
    i7-4770k - GTX 780 Ti - 16GB DDR3 Ripjaws - (2) HyperX 120s / Vertex 3 120
    ASRock Extreme3 - Sennheiser Momentums - Xonar DG - EVGA Supernova 650G - Corsair H80i

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  4. #4
    A single 12V rail @ 25A = 300W. No 7970 draws 300W.
    Intel i5 2500K (4.5 GHz) | Asus Z77 Sabertooth | 8GB Corsair Vengeance LP 1600MHz | Gigabyte Windforcex3 HD 7950 | Crucial M4 128GB | Crucial M550 256GB | Asus Xonar DGX | Samson SR 850 | Zalman ZM-Mic1 | Western Digital Caviar Black 2000GB | Noctua NH-U12P SE2 | Fractal Design Arc Midi | Corsair HX650

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  5. #5
    Quote Originally Posted by Butler Log View Post
    A single 12V rail @ 25A = 300W. No 7970 draws 300W.
    Yep..

    I took some measurements awhile ago and my system load at idle was around 250w and firing furmark up the total load was around 400-450w. I always use fixed mode voltage and disabling power options with 1.5Vcore so.

    Just a question two 12V rails 25a per, means 50a so you have a 600w psu?

  6. #6
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    My whole system with a 7970 draws less than 360W from the wall with ~92% efficiency.

  7. #7
    Quote Originally Posted by Faithh View Post
    Yep..

    I took some measurements awhile ago and my system load at idle was around 250w and firing furmark up the total load was around 400-450w. I always use fixed mode voltage and disabling power options with 1.5Vcore so.

    Just a question two 12V rails 25a per, means 50a so you have a 600w psu?
    What kind of monster system are you running at 250W idle usage?
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  8. #8
    I ask because I do GPU accelerated rendering from time to time, which in theory should push my PSU somewhat close to its limit. Not to mention the card I ordered is factory OC'd. I've just seen numbers such as:

    http://www.techpowerup.com/reviews/AMD/HD_7970/26.html

    I'd rather not have the 12v rail at 270w of the 300w capacity. I suppose the main question is, do PCI sockets still provide -some- power when you have PCI power connectors connected? Or is that a thing of the past?

    ---------- Post added 2013-02-06 at 09:16 PM ----------

    Quote Originally Posted by n0cturnal View Post
    What kind of monster system are you running at 250W idle usage?
    I don't think any (consumer) system configuration on the planet uses 250w at idle. <.<
    i7-4770k - GTX 780 Ti - 16GB DDR3 Ripjaws - (2) HyperX 120s / Vertex 3 120
    ASRock Extreme3 - Sennheiser Momentums - Xonar DG - EVGA Supernova 650G - Corsair H80i

    build pics

  9. #9
    Quote Originally Posted by n0cturnal View Post
    What kind of monster system are you running at 250W idle usage?
    A PC I think?

    Well I just used 350mhz on vrm, 140% cpu power thingie, 1.5Vcore manual fixed mode, disabled all C states crap, full phase vrm and something else is set to extreme as well. I have like uhm 10 casefans atm + H100 + 7200rpm hdd which is running all the time. A gpu idling at ~20% tdp and IGP is enabled as well.

  10. #10
    Disabling the features that allow a computer to "idle" doesn't make not doing anything = idle
    Intel i5 2500K (4.5 GHz) | Asus Z77 Sabertooth | 8GB Corsair Vengeance LP 1600MHz | Gigabyte Windforcex3 HD 7950 | Crucial M4 128GB | Crucial M550 256GB | Asus Xonar DGX | Samson SR 850 | Zalman ZM-Mic1 | Western Digital Caviar Black 2000GB | Noctua NH-U12P SE2 | Fractal Design Arc Midi | Corsair HX650

    Tanking with the Blessing of Kings - The TankSpot Guide to the Protection Paladin - Updated for Patch 5.4!

  11. #11
    Quote Originally Posted by glo View Post
    I suppose the main question is, do PCI sockets still provide -some- power when you have PCI power connectors connected? Or is that a thing of the past?[COLOR="red"]
    A single pair is 25W, so 6pin = 75w -> HD 4850 has 1 6pin plug & takes 75W from the board which makes the card use max if it needs to 150W. If you have 2x 6pin plugs it will take 150W max. In my case my gtx 680 which has a 8pin + 6pin so this makes 75W+100W = 175W from the PSU and can take 75W from the board.

    They still should provide power, I mean if you plug a network card into a pci express port, the nic is still going to need power.

  12. #12
    Quote Originally Posted by glo View Post
    I ask because I do GPU accelerated rendering from time to time, which in theory should push my PSU somewhat close to its limit. Not to mention the card I ordered is factory OC'd. I've just seen numbers such as:

    http://www.techpowerup.com/reviews/AMD/HD_7970/26.html

    I'd rather not have the 12v rail at 270w of the 300w capacity. I suppose the main question is, do PCI sockets still provide -some- power when you have PCI power connectors connected? Or is that a thing of the past?
    Isnt another possibility to just hook it up to both lines? I have no idea if this a smart thing to do, i just have a single rail PSU (much easier in this regard ;P)

  13. #13
    Quote Originally Posted by Zeara View Post
    Isnt another possibility to just hook it up to both lines? I have no idea if this a smart thing to do, i just have a single rail PSU (much easier in this regard ;P)
    Most multi railed psu's, take the 12V rails are acting as one. There are some exclusive psu's like each 12V has it's own source.

  14. #14
    Quote Originally Posted by Faithh View Post
    Most multi railed psu's, take the 12V rails are acting as one. There are some exclusive psu's like each 12V has it's own source.
    Vast majority of multirail PSUs don't combine rails, each rail has its own regulator and auto cutoff switch. Not sure where you're getting that idea from.
    i7-4770k - GTX 780 Ti - 16GB DDR3 Ripjaws - (2) HyperX 120s / Vertex 3 120
    ASRock Extreme3 - Sennheiser Momentums - Xonar DG - EVGA Supernova 650G - Corsair H80i

    build pics

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