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Corsair 850W enough for Twin HD 5870 + GTX 275 for PhysX and 1090T@3.8ghz

Discussion in 'System Builder's Advice' started by bpgt64, Jun 30, 2010.

  1. bpgt64

    bpgt64

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    Full system specs are to the side. But the title says it all. Is a Corsair 850W PSU enough for a 3.8ghz AMD 1090T, and HD 5870 x2, and a GTX 275 for PhysX?
  2. cadaveca

    cadaveca My name is Dave

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    I'm pulling about 650w with 5870 Crossfire, so I'd recommend you step up to 1000w if adding the 275.
  3. bpgt64

    bpgt64

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    Hrm...if thats the case, I may just sell the GTX 275
  4. TIGR

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    If memory serves (someone correct me if I'm wrong), those three cards, overclocked and at max load, will pull a combined 450-500w. I understand the 1090T can draw quite a bit of juice when overclocked but haven't measured it myself. I think you're going to be safe, but if you ever load the CPU and GPUs to 100%, and if you have a lot of other "stuff" plugged into the system, you could approach 800-850 watts of DC draw.

    Do you have an 850HX or 850TX? The HX has been shown to be good for 1000w (link).
    drdaver, coljarcker and Soylent Joe say thanks.
  5. bpgt64

    bpgt64

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    99% sure its a TX, as its not Modular.

    But the GTX 275 isn't going to be running full boar, it isn't going to be powering any moniters even. PhysX taxes it THAT much?
  6. TIGR

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    No, as a PhysX card the 275 isn't going to be running anywhere near 100%. For PhysX, it's such overkill that I guessed you would probably also be using it for something like Folding@home, which would load it to 100%. You should definitely use it to fold for TPU. ;)

    Anyway, yes you have the 850TX then, and I'm not sure how much over 850w it can put out, but HardwareSecrets got 900w out of the 750TX, and 990w out of the 950TX. All three are made by CWT and I believe the 850TX is closer in design to the 750TX.
  7. bpgt64

    bpgt64

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    Yes it...super overkill. But I have a GTX 275, I don't have a GTS 240. Might have to sell it though..
  8. twistedspark

    twistedspark New Member

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    The total TDP for those 3 GPUs and that CPU is (188 x 2) + 219 + 125= 720W
    Your PSU is NOT 850 Watts. It's called a TX850W, but it's rated at 850 Volt Amperes, not Watts. With their claimed 80% efficiency, and 850VA, the PSU will supply a maximum of 680 Watts. So no, your TX850W isn't enough.
  9. erocker

    erocker Super Moderator Staff Member

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    Where is this data? You're doing something wrong. Everything I've seen from them has been listed as 80% efficiency and 850 watts. I've pulled over 700 watts under load as well (a 680 watt PSU could do that at peak) and it didn't seem to stress the PSU in any way.
    Last edited: Jul 6, 2010
  10. twistedspark

    twistedspark New Member

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    The efficiency of an electrical device is multiplied by the rated VA to determine wattage. In a perfect setting with no resistance an electrical device with 100% efficiency and a nameplate rating of 850 watts would produce just that, 850W. With 80% efficiency it would produce 680W. As temperatures and resistance climb, efficiency drops. You can pull more power than the device is rated for, sure, but at increased risk of failure and/or fire. If someone's planning on building a folding PC that'll be working 24/7...even when no one's home, I think it would be smart to remain under the rated limit.
    Last edited: Jul 3, 2010
  11. erocker

    erocker Super Moderator Staff Member

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    Last edited: Jul 3, 2010
  12. bpgt64

    bpgt64

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    It should never matter. When the GPU'z are running, rarely are more than 3 cores being used. And when all the cores are in use, the GPUs are usually Idle. It will see 100% full load less than 10% of its overall active time. The GTX 275 will never pull its full TDP just doing Hardware accellerated PhysX either.

    The ONLY thing that holds me back from doing this immediately, is that I don't have the money in hand to replace the 275 with a 465..and I might wait for a used 465. And I (yes I have seen the TPU testing about 8x channels) but both 5870s are in X16 right now, and if I plug in another device, they'll roll back to x16x8x8
  13. erocker

    erocker Super Moderator Staff Member

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    Why would you want or need either for PhysX? Get something smaller that requires no power connector. With a GT240 I can play games like Batman with PhysX on it's highest setting.
  14. bpgt64

    bpgt64

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    Sorry, should have elaborated. With the DX11 WoW update, my wife wants a DX11 GPU, I am taking the GTX 275, and giving her a 465. I agree with you about the GT240, but I have a 275 in hand is what I am saying.
  15. newtekie1

    newtekie1 Semi-Retired Folder

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    That is not how efficiency and power supplies work, I don't now where you are getting this information, but it is wrong.

    The Corsair, is rated at 850w. That means it can provide 850w to the components in the computer. This does not mean it pulls 850w from the AC outlet. You don't take 850w from the wall and rate it down to get what the PSU is capable of. The PSU is capable of 850w, the efficiency means it pulls more than that from the wall. So an 850w PSU will be pulling about 1000w from the wall under full load, assuming 85% efficiency.
    Crunching for Team TPU 50 Million points folded for TPU
  16. onepost

    onepost New Member

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    just use this- i put in my best guess for your system and it maxed at 700watts
  17. IINexusII

    IINexusII

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    i would sell your 275 and get something less powerful if youre just using it for physX
  18. erocker

    erocker Super Moderator Staff Member

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    You can try. The only thing I'd be worried about is supplying enough power using the molex to 6 pin adapters. Even then it should work.

    I used (and it worked)

    965BE 4ghz
    two 5850's 950/1200 (very slight increase in voltage)
    GTS 250
    plus water cooling, fans and everything else.

    ..using the tx850w.
  19. Benetanegia

    Benetanegia New Member

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    Exactly, I don't know from where his info came from, but it's totally wrong.

    I'd wait for the GTX260 if you want to go with Nvidia. You just have to wait a week or so now. Better prices, much better power consumption and I'm actually expecting it to be slightly faster than 465 except at uber-high resolution +AA where it may be slower but not much either.

    Basically 336 SP * 675 Mhz >> 352 SP * 607 Mhz.

    EDIT: Actually the 256 bit 460 will be faster in every posible way and still cheaper I think.
    Last edited: Jul 6, 2010
  20. TIGR

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    Just want to back up those who say the Corsair is good for 850w, not 80% of 850w.

    PSUs are rated according to their DC output, not their AC input [with no exceptions that I know of]. A PSU that is rated for 850w and which is 80% efficient, can draw ~1063w of AC power and put out 850w of DC power[1].

    Also note that PSUs are [all, to the best of my knowledge] rated in watts, not VA (volt amps). The ratio of watts to VA is called the power factor and that is what "PFC" (power factor correction) on PSUs is all about. Where you may have accurately heard about VA vs watts really coming into play is when sizing a UPS (Uninterruptible Power Supply), as a UPS must be able to handle both the "VA" and the "watts" load drawn from it.

    [1] - note that this assumes that the PSU's rating is accurate. Many PSUs can't provide their rated power while staying within voltage regulation and noise/ripple specs. Conversely, many other PSUs can provide more than their rated power while staying within spec. The Corsair 850TX is a good example of the latter.
  21. twistedspark

    twistedspark New Member

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    You're exactly right. Yeah, I was wrong. I was thinking of the issues I dealt with with folding from my 4 gpus overloading my UPS. That's exactly what it was. I got the two mixed up. I turned off my PC and examined the psu and it is rated in Watts, not VA.
    :ohwell:
    TIGR says thanks.
  22. Benetanegia

    Benetanegia New Member

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    I was suspecting that.

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