Video Card Power Consumption FAQ

Discussion in 'Video Cards' started by evilsofa, Dec 12, 2008.

  1. evilsofa

    evilsofa [H]ardForum Junkie

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    I see many questions about whether a PSU is enough to drive a video card. I get the feeling that people generally think video cards use much more power than they actually do. Let's review some basic facts:

    A PCI-E 1.x motherboard delivers a maximum of 75W to each PCI-E 1.x slot.
    A PCI-E 2.0 motherboard delivers a maximum of 150W to each PCI-E 2.0 slot.
    Each 6-pin PCI-E power connector delivers a maximum of 75W to the video card.
    Each 8-pin PCI-E power connector delivers a maximum of 150W to the video card.

    Watts = Volts x amps
    Video cards are run on the 12v rail, so for our purposes, Amps = Watts / 12

    Therefore:
    The most a video card that requires no power connectors can pull under any circumstances is 150W, or 12.5 amps.
    The most a video card that requires one 6-pin PCI-E power connector can pull under any circumstances is 225W, or 18.75 amps.
    The most a video card that requires two 6-pin PCI-E power connectors can pull under any circumstances is 300W, or 25 amps.
    The most a video card that requires one 6-pin PCI-E power connector and one 8-pin PCI-E power connector can pull under any circumstances is 375W, or 31.25 amps.

    Most video cards actually pull far, far less than these maximum amounts. Note that video card makers must still assume that the user might want to run the card on a PCI-E 1.x motherboard, so they cannot assume that extra 75W from the PCI-E 2.0 slot will be there.

    The above statements are fact, and not open to debate. When you ask how much a specific video card actually pulls, it gets much more debatable, because as far as I know, nVidia and ATi don't officially state how much wattage their reference card designs pull. You have to search around and find articles where reviewers have deduced how much power the video card consumes.

    Below I list some video cards and the amount of wattage that reviewers say they use under full load. I list standard reference clock speeds only; overclocked cards will use more power (sometimes much more) and there are too many of those to list each one. Wattages listed are for the card only, not for the entire system.

    Disclaimer: This list is only as trustworthy as the reviewers quoted. Sometimes the reviewers agree (see the 4850 entries), sometimes they disagree (note the GTX260 192 entries). I didn't make any of these measurements, nor would I know how to. Sources are listed in parenthesis. I may add more as I find them or have them pointed out to me.

    nVidia GTX280: 178W, or 14.8 amps (XBitLabs)
    nVidia GTX260 (192 stream processors): 122W, or 10.2 amps. (SPCR)
    nVidia GTX260 (192 stream processors): 136W, or 11.3 amps (XBitLabs)
    nVidia 9800GX2: 182W, or 15.2 amps (XBitLabs)
    nVidia 9800GTX+ (two 6-pin PCI-E power connectors): 114W, or 9.5 amps (XBitLabs)
    nVidia 9800GTX+ (one 6-pin PCI-E power connector): 80W, or 6.7 amps (XBitLabs)
    nVidia 9800GTX: 108W, or 9 amps (XBitLabs)
    nVidia 9800GT: 83W, or 6.9 amps (XBitLabs)
    nVidia 8800GT: 78W, or 6.5 amps (XBitLabs)
    nVidia 9600GT: 60W, or 5 amps (XBitLabs)
    nVidia 8800GTS 512MB: 99W, or 8.25 amps (XBitLabs)
    nVidia 8600GTS: 47W, or 3.9 amps

    ATi 4870X2: 264W, or 22 amps (XBitLabs)
    ATi 4870: 130W, or 10.8 amps (XBitLabs)
    ATi 4850: 101W, or 8.4 amps (SPCR) (XBitLabs)
    ATi 4830: 85W, or 7.1 amps (XBitLabs)
    ATi 3870X2: 171W, or 14.25 amps (XBitLabs)
    ATi 3870: 81W, or 6.75 amps (XBitLabs)
    ATi 3850: 63W, or 5.25 amps (XBitLabs)
    ATi 4670: 47W, or 3.9 amps (XBitLabs)
    ATi 2900xt: 161W, or 13.4 amps (XBitLabs)
    ATi 2600xt: 49W, or 4.1 amps (XBitLabs)
    ATi x1950xtx: 110W, or 9.2 amps (SPCR)

    Don't forget that your CPU uses power from the 12v rail as well. (I welcome comments on how much.)
    Overclocked video cards can use much more power than the standard reference cards, but most cards will probably artifact or crash long before they hit the slot+connector maximum wattages.
     
  2. Valset

    Valset [H]ardness Supreme

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    nice post, sticky material?
     
  3. n00zler

    n00zler Limp Gawd

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    Thanks! I've been trying to figure out what power supply to pick up for an SLi rig I'm building. Good to be able to refer to something :)
     
  4. needmorecarnitine

    needmorecarnitine [H]ardness Supreme

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    Are all motherboards with PCI-E 2.0 capable of delivering up to 150W to the slot or are you citing what the spec says? (Do motherboard makers need to "certify" their boards or can they just label it 2.0?)
     
  5. evilsofa

    evilsofa [H]ardForum Junkie

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    If a motherboard's power delivery system is out of spec, then I would think it should neither be bought nor sold.
     
  6. AreEss

    AreEss 2[H]4U

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    http://www.pcisig.com/specifications/pciexpress/compliance/compliance_library#electrical20

    They are decidedly not guaranteed capable of delivering up to 150W sustained. PCIe 2.0 Electrical and Physical tests DO NOT test whether a physical card slot or chipset is capable of 150W of power. The PCIe specification defines power limits and does not define or test actual power delivery.

    Motherboard manufacturers do NOT certify boards, but instead rely on chipset certification. i.e. Joe's Motherboard Shop can make an Intel X58 board and slap the PCIe 2.0 label on it at will, even though his 12v regulation can only handle 150W combined total.
     
  7. Elledan

    Elledan [H]ard|DCer of the Month - April 2010

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    Very informative, thanks :)
     
  8. kniah

    kniah 2[H]4U

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    thanks, excellent post.
     
  9. Mnx4

    Mnx4 [H]ard|Gawd

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    Is there a typo between the two 260's listed? That is, should one of them be 216? Only wondering because the voltage is different between the two, but there isn't a reason listed for that to be the case.
     
  10. evilsofa

    evilsofa [H]ardForum Junkie

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    SPCR (silentpcreview.com) and XBitLabs (xbitlabs.com) reviewed GTX260 192 cards and came up with different answers on power consumption. It was interesting to see those two sites agree on the 4850's power consumption and disagree on the GTX260 192's power consumption, because as far as I can tell, both of the GTX260 192 cards were reference designs.
     
  11. ZenOps

    ZenOps 2[H]4U

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    I hate that videocard manufacturers still do not even print generalized wattage specs for their chips, nevermind whole card lines.

    It makes it really hard to right-size a power supply.
     
  12. bAMtan2

    bAMtan2 [H]ard|Gawd

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    wow Video Card Power Consumption FAQ

    sticky please

    bump

    informative post

    sticky please

    good post
     
  13. evilsofa

    evilsofa [H]ardForum Junkie

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    I'm not sure anymore how valid some of this data is.
     
  14. HardLiner

    HardLiner Gawd

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    How much do you think my power supply handle 4870?......4870X2 probably not?


    Corsair VX550W 550W ATX 12V 41A 24PIN
     
  15. Oldie

    Oldie Mean Old Administrator Staff Member

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    If someone is willing to put the leg work into making sure this is up to date, PM me when you're done and I think we can sticky it for a bit.
     
  16. evilsofa

    evilsofa [H]ardForum Junkie

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    One thing that concerns me is that it has become clear that different review sites are using different methods for measuring how much power a card uses at maximum. In particular, HardOCP has recently changed its measurement method by using Furmark.

    I also just noticed that when I originally posted this, I thought there was 65nm versions of the 9800GTX+, which in fact there wasn't - they are all 55nm. But some 9800GTX+ cards do require two 6-pin connectors while some require only one.
     
  17. bmoney9

    bmoney9 Limp Gawd

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    how much does a 4850x2 take?
     
  18. evilsofa

    evilsofa [H]ardForum Junkie

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    I don't know, but if you look at the known power consumption of the 4850, 4870 and 4870X2, I'd be surprised if it was far different from 205W. But I hasten to add that I haven't seen any reviews that remarked on the power consumption of the 4850X2.