How does a PC power supply actually work?

Lets say I have a 400 watt power supply. And I have a 400 watt video card, 50 watt motherboard and 100 watt processor. That makes 550 watt. Right? So does that mean that my 400 watt power supply can't handle it and I need to buy a new power supply or will everything be OK because it's all 400 watt or under.

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  • Anonymous
    1 decade ago
    Favorite Answer

    Yes your power supply should be rated to supply enough power (plus ~20% more) to cover the power draw from all the PC's components. It may work with a smaller one but you will eventualy run into problems. Also in the equation you have to consider the draw from equipment used on your usb ports ( scanners etc) One more thing with power supply spec's some are rated diferantly!! Some are specification rated and some are not....meaning a non spec rated may say 500 watts but actually be 400W and a spec rated one that maybe used by government or hospitals and IT etc would reach 100% of the rating stated , but may cost a little more.

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  • Gordon
    Lv 6
    1 decade ago

    You have to add everything up. So in your case, the 400 Watt power supply would be inadequate. BTW, you should never run a power supply at or near it's rated output. Give the thing at least 20% headroom.

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  • Anonymous
    1 decade ago

    Sounds like you need a higher wattage p/s.

    Long ago I saw a graphics card that came with a 12volt adapter to plug into the wall and into the edge of the card. Seems the card manufacturer didn't want to load down the pc p/s too much.

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