Can my PSU take a HD4870?

Discussion in 'Videocards - AMD Radeon' started by Zareph, Jun 30, 2008.

  1. Anarion

    Anarion Ancient Guru

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    Yeah. I think this is why Antec does not mention the combined +12V output power.
     
  2. Zareph

    Zareph Ancient Guru

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    Yes, that would be logical, but everywhere it does say it's dual rails, but I have never actually seen a review of this thing... So can you tell me where you found that information you quoted earlier mate?
    And if it is the case of it being a single rail PSU, I must thank you for having enlightened me.
     
  3. Anarion

    Anarion Ancient Guru

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  4. Makalu

    Makalu Ancient Guru

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    erm lol well PSU labels do often lie about many things including the number of rails. But anyway it's a dual-rail unit that follows the original Intel Guide for dual rail units and puts the CPU power connector on one rail by itself and all of the other connectors on the other rail.

    The combined 12V is not given on the label nor in the Antec literature. The combined 3.3V and 5V is given and we can know that the 12V combined is at least 27A by subtracting that...but individual rail over-current limits don't tell us anything at all about what the unit can output. I'm not sure why xbitlabs said that it's 36A because they didn't put quite that much on the load test and they usually take a PSU up to the 12V rating but anyway it's clear that it will do 35A (420W) on the 12V's...figure though that the CPU connector uses about 10A on average so that would mean that only about 28A is available in a typical system configuration (with about 8A being unusable on the CPU rail).

    I still say it'll work...barely :)
     

  5. Makalu

    Makalu Ancient Guru

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    yeah...no problem there.
     
  6. Zareph

    Zareph Ancient Guru

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    Makalu, you confuse me. Where did you get those 35A and 420W from?
     
  7. Makalu

    Makalu Ancient Guru

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    oh sorry...see the crossload graph here:

    http://www.xbitlabs.com/images/other/antec-psu-roundup/2gr2.gif

    that's the results of actual loads placed on the PSU with a load tester (as opposed to loading it with a computer system). The combined 12V load goes left to right and the combined 3.3V and 5V load goes bottom to top and it looks to me like the maximum amount they loaded the 12V's was just about 420W (420W/12V=35A)
     
  8. jimmy545

    jimmy545 Member Guru

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    Hey Makalu,

    How would you rank these 3 in terms of power consumption?
    hd4870
    gtx260
    8800gtx
    I've seen lots of conflicting info

    Thanx
    Jimmy
     
  9. Makalu

    Makalu Ancient Guru

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    oh I figure about 120W for an HD4870, about 130W for an 8800GTX and about 150W for a GTX260...I could easily be wrong 10-15 watts in either direction (plus or minus) but I don't think that 12W (1A) is enough to worry about when making a PSU decision. Temperature changes alone will vary PSU output by more than that.
     
  10. jimmy545

    jimmy545 Member Guru

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    cool thanx for that
     

  11. jimmy545

    jimmy545 Member Guru

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    Makalu,

    sorry man, just remembered this - why do you think Hilbert conflicts with what you say?

    http://www.guru3d.com/article/geforce-gtx-260-review/4 (7th para)

    http://www.guru3d.com/article/radeon-hd-4870-review--asus/5 (1st para)

    "Our test system contains a Core 2 Duo X6800 Extreme Processor, the nForce 680i mainboard, a passive water-cooling solution on the CPU, DVD-rom and a WD Raptor drive. The results:
    PC in Idle = 159 Watt
    PC 100% usage (wattage gaming Peak) = 302 Watt"


    "Our single card test system is a Core 2 Duo X6800 Extreme Processor, the nForce 680i SLI mainboard, a passive water-cooling solution on the CPU, 2GB memory, DVD-ROM and WD Raptor drive. Have a look:

    Radeon HD 4870 334 Watt"

    Jimmy
     
  12. mintor

    mintor Member

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    500 too small. need 32, amps on 12 v rail
     
  13. mintor

    mintor Member

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    In my view the Radeon HD 4870 series requires you to have a 500 Watt power supply unit at minimum if you use it in a high-end system, and I think that's barely on the safe side. Also recommended is 32 AMP's on the 12 volts rails for stable power distribution (in a single card configuration). Please make note of the fact that the card uses two 6-pin power connectors
     
  14. Makalu

    Makalu Ancient Guru

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    Well the estimates that I listed are for the card alone and Hilberts and all the other reviewers are listing total system consumption. Also I'm estimating DC consumption for the card and these reviews are listing AC input for the system using Kill-A-Watt type devices between the PSU and the wall. So, for instance, the PSU that Hilbert uses has an energy efficiency of approximately 83% so his measurement of 334W for the HD4870 system works out to about 277W DC load...and I estimate about 120W of that is from the GPU. I'm estimating GPU consumption by looking at Hilberts and others reviews with their AC input measurements and then looking at other measurements made by the same reviewer that are for cards that the consumption is known and then extrapolating from that.

    I'm maybe a little low there for that one...could easily be 130W for an HD4870 alone but like I said I don't quibble over an amp here or there.
     
    Last edited: Jun 30, 2008
  15. Makalu

    Makalu Ancient Guru

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    oh wait...I see what you are saying...Hilbert measured about 30W more with the HD4870 then he did with the GTX260. I dunno man...I'm home recovering from surgery this morning and will take a closer look at his figures and others later when I feel better ok? lol sorry

    It would help if I knew for sure which PSU he used in all these tests but he rarely lists it. I know that he's used an Enermax Galaxy 1000, a Sirtec/HighPower 1200 and a BFG ES800 in the test system in the past and the difference in efficiency between the Enermax and the BFG adds up to about 20W at these load levels so anyway...hard to pinpoint it off his reviews alone with the info given.
     
    Last edited: Jul 1, 2008

  16. Makalu

    Makalu Ancient Guru

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    ok well I took a look at some other reviewers measurements and they all lead me to believe that HD4870 consumption is between 120W and 140W for the card alone and Hilbert's measurements with it exceeding a GTX260 really just don't jive with the others. Dunno if that is due to a factory deviation or PSU efficiency or it could even be due to a brown-out type condition on his AC line.
     
  17. jimmy545

    jimmy545 Member Guru

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    ok thanx a lot, I guess different psu's must be the explanation - I was pretty sure 4870 sucked slightly less power than 260

    all the best with your recovery!

    EDIT: Ha you beat me by 60 secs - yeah thats what I figured
     
    Last edited: Jul 1, 2008
  18. Zareph

    Zareph Ancient Guru

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    If there was a point system, I'd give you -reputation.
    It says 450watt on the ATI website, the question is the amps. And it seems I have 36A on the 12v rail, so please read replies before commenting...
     
  19. xBeldin

    xBeldin Master Guru

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    You need to start saving your pennies for a PSU upgrade Peezee.
     
  20. Anarion

    Anarion Ancient Guru

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    I doubt that. He apparently have ~36A on +12V rail.
     

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