How large of a PSU do I need?

Building a computer and was wondering how many Watts i need to power it? I know practically nothing about computers, just designed this one due to available funds/ what Ive read about on the internet.
Plan on using:
AMD Phenom II X4 955 BE processor
ASUS M4A79T Deluxe motherboard
ATI Radeon 5770 1024mb video card (Want to purchase a 2nd one of these eventually)
Seagate Barracuda 300GB 7200 harddrive
Zalman CNPS9500 heatsink
(undecided on the DDR3 RAM-suggestions for the current set up would be appreciated)

The problems i have run into while trying to figure out how many watts are needed is that different sites state different numbers for the power requirements of the processor and other pieces. So if you can help me out with my dilemma i would be very appreciative.
9 answers Last reply
More about large need
  1. A decent 650w power suplly will be great. You probably should get one that is cross fire certified.
  2. I have an old 500W Enermax Liberty from another that enough or is 650 pretty much required for all the stuff?
  3. the 500 should be enough for the single GPU but you will need at about 600w for the crossfire setup; hence the 650w recommendation, i dont see 600w ones too often 650 seems to be more of a standard
  4. This will "do the math" for you

    This will help you pick it
  5. Awesome. Thanks for the help fellas :D.
  6. Here are the ATI recommended power supply requirements for the ATI Radeon HD 5770 and 5750 video cards:

    450 Watt or greater power supply with one 75 watt, 6-pin PCI Express® power connector recommended

    600 Watt or greater power supply with two 75 watt, 6-pin PCI Express® power connectors for ATI CrossFireX™ technology in dual mode.

    The recommendations are for an entire pc system..

    Corsair and Seasonic are two brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty.
  7. 450 to 500 watt PSU will be more then enough to run it your PSU will be fine just make sure you have a PCIE connector on that PSU if not you can get adapters but I hate adapters but they do work. For crossfire 550 to 600 watts will do as long as its a quality unit the manufactures recommended wattage is inflated to account for sub par PSU.

    Corsair and Seasonic are great units like Johnny said I like Antec units too they have some great reliable PSU's.
  8. I do NOT need to purchase a new PSU to run the system mentioned above with 2 Radeon 5770's?

    lmao nvm...misread that last response.
  9. For two 5770's, I'd use a Corsair 650TX (52 amp 12 volt rail):
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