Need PSU Wattage advice for my homebuilt system


GTW - 158W up to 320W
AMD 125 W
Mem 8/20 - 65W [1-98-682-709 (john)]
DVD/CD 20W - 30W
Hard Drive 15W - 30W
Average PCI Card 5W - 10W

Motherboard (w/o CPU or RAM) 50W - 150W
Case/CPU Fans 3W (ea.)

750W - 800W with everything maxed out.

Hello Everyone,

I'm building the following system and I'm trying to figure how much power I need to run it:

Motherboard: GIGABYTE GA-MA770T-UD3P

+Graphics Card: eVGA nVidia 8800 GTX 712mb /w the cooler/sync: Arctic Accelero X8800
+ CPU: AMD Phenom II 940 BE (3.0GHz factory but will overclock to 3.7GHz when gaming) /w cooler/sync: Arctic Freezer 64 Pro
+ Memory: 4GB DDR3 Kingston 1333MHz (2 modules)
+1 Computer Fan
+ 1 SATA 1TB drive
+ 1 or 2 ATA drives
+ 1 DVD/CD Burner
+ 1 HongKong-Bought 5.25' internal card read, USB-Firewire Bay
+ 1 PCI Wifi card
+ 1 PCI modem card

I would like to spend the minimum amount on power supplies without compromising this system I've taken so much pain to research, purchase the parts and assemble. I'm currently looking at the OCZ 750W GameXStream on ebay. The 750W is relatively cheap, the 850W jump to double or 50% over the 750W cost. If I can get away with the 750W or even the 600, I would much prefer that.

As I understand it, the 750W rating is PEAK and that I shouldn't be running the computer that often anywhere near that (OCZ techie told me to run it at 80% which would leave me a continuous operating level of 600W with a 150W grace zone).

I'm less worried about normal operation and more about the 4 or 5 hours of gaming that I'd do with the graphics card not getting enough juice, the game crashing, turning sluggish or the box shutting down b/c it's overloaded.

Could anyone give me some feedback?
As to how much I need?
Thanks! Fadi
9 answers Last reply
More about need wattage advice homebuilt system
  1. A decent 500W PSU will be enough. Antec, Corsair, PC Power & Cooling, Seasonic, and Enermax are among the better brands. Choose one that has full range active PFC and is 80+ certified.
  2. Good sites for reviews on PSUs are or

    I opted for the Corsair 450VX after pricing PSUs around and reading this review:
    The same unit can still be had for $55 after rebate:
  3. ^5 +1 what jit283 said.

    Your system is not a power hog. The Corsair VX450 mentioned by ekoostik can power your system. There is more than enough current (amps) on the 12 volt rail to easily handle an 8800 GTX video card.
  4. zipzoomflyhigh - about that upgrade - Have you read the technical reviews for the ATI Radeon HD 5870? They are pretty efficient cards. Anantech did an excellent review and they measured total power consumption at the wall outlet (mains) for an Intel Core i7 920 2.66 Ghz system overclocked to 3.33 Ghz with a single 5870 while playing World of Warcarft. They also did a second test with two 5870's operating in Crossfire mode. Total power draw for one video card was 295 watts. Total power draw with two 5870's was 430 watts.

    The results for one video card were consistent with the results published in a Tom's Hardware article last January that also showed power consumption during gaming. The typical gamer uses a little less than 300 watts during a gaming session. Here we have an overclocked Core i7 920 and a brand new high end video card doing the same. The 5870 uses about 10% less power than current generation cards.

    We also have more energy efficient cpu's and gpu's coming based on new 32nm technology that will require even less power. Intel just did a show and tell presentation of one of those new cpu's. The future will see us using less energy rather than more.
  5. zip - The Intel Core i7 920 was definitely overclocked to 3.33 Ghz. The total draw at the wall outlet for the entire system with one 5870 was only 295 watts during a gaming session. The psu in the overclocked system drew less power than the 318 watts at stock settings which you suggested. How can a overclocked system during a gaming session use less power than the rated power? In fact, how can an overlocked system at idle use only 27 watts instead of the rated 318 watts? Pretty simple - The numbers you quoted do not reflect actual usage.
  6. I know an easy way to settle this, other than reading those reviews. I just happen to own a Corsair 450VX. Now if someone would send me an i7 920, mother board, and 5870 I would be more than happy to report back my findings.
  7. ekoostik - LOL :)
  8. Now that was funny.
  9. I would recommend that you stay at 600-700W rate in case you need to add additional hardware/components.

    I bought my PS (Seasonic) 500W morethan 3 yrs ago and I could still use it with a HD4xxx ATI because it has SLI...

    You need to think a couple of steps in the future but of course you don't want to end up buying very expensive P.S.
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