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Is my PSU powerful enough for my graphics card?

I use an old Dell server as my desktop and it works great, except the onboard video is shocking!

The computer is notorious for being fussy with graphics cards but the BFG 8800gt apparently works well, so I bought one.

The computer POSTs and will go into BIOS but it won't load an operating system, not even from a USB stick.

I have read that the 8800gt only consumes up to 225w but it needs 24-28amps on the 12v rail.

My PSU is 750w but i'm confused about the ampres. The sticker on the PSU mentions +12v four times (VA,B,C and D) and on three of them it says 18a and on one it says 16a.

Does this mean my max current at 12v is only 18a? And hence likely the reason for my crashes when I try to boot up?
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  1. devavictrix said:
    I use an old Dell server as my desktop and it works great, except the onboard video is shocking!

    The computer is notorious for being fussy with graphics cards but the BFG 8800gt apparently works well, so I bought one.

    The computer POSTs and will go into BIOS but it won't load an operating system, not even from a USB stick.

    I have read that the 8800gt only consumes up to 225w but it needs 24-28amps on the 12v rail.

    My PSU is 750w but i'm confused about the ampres. The sticker on the PSU mentions +12v four times (VA,B,C and D) and on three of them it says 18a and on one it says 16a.

    Does this mean my max current at 12v is only 18a? And hence likely the reason for my crashes when I try to boot up?


    I don't know where you read that but it's wrong.

    http://www.geforce.com/hardware/desktop-gpus/geforce-8800-gt/specifications
  2. Ive just re-read the forum and I overlooked that it was the total power consumption (for the whole system), not the graphics card.

    I suppose my question is more related to PSUs that the graphics card.

    My understanding is that if you have a single 12v rail then you need 24-28amps and if you have multiple 12v rails then you can just add up the current ratings on each rail because many 'multiple rail' PSUs are actually a single rail that is split. But PSUs exist that are true multiple rail and in is case you cannot add up the current ratings. Is there any way of finding out if I have a true multiple rail PSU?
  3. Best answer
    devavictrix said:
    Ive just re-read the forum and I overlooked that it was the total power consumption (for the whole system), not the graphics card.

    I suppose my question is more related to PSUs that the graphics card.

    My understanding is that if you have a single 12v rail then you need 24-28amps and if you have multiple 12v rails then you can just add up the current ratings on each rail because many 'multiple rail' PSUs are actually a single rail that is split. But PSUs exist that are true multiple rail and in is case you cannot add up the current ratings. Is there any way of finding out if I have a true multiple rail PSU?


    Open it up and see if all the power leads originate from a single point or multiple points.
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