Originally posted by: myocardia
Originally posted by: Howard
Christ, where are some of you people getting your figures from?
Fact: TDP of the 8800GTX is ~180W, meaning the worst case current draw will be 180/12 = 15A. In current systems, they're drawing more like 13A (but 15A is the number that should be allocated). Two of those and you get 30A draw for the video cards.
Processor - 5-11A (C2Ds are 5-7A)
Mobo - ~3A depending on the devices connected to it, how much memory, onboard sound/video, etc.
Video - 30A
HD - ~0.5A per
Optical drive - ~1A per
Misc. PCI cards - 0.5-1A per
Fans - 0.2-0.4A per (says on the hub sticker)
For a conventional rig with a C2D at ~3GHz, 2 HDs, 1 optical drive, 2 8800GTX cards, and two fans, that adds up to 42.6A. A PSU at 45A would be fine, although the cheapest one I'd recommend is the Corsair CMPSU-620HX with 50A. Perfect.
Howard, the reason we're arguing is because a)your numbers look about right, but forget to factor in the known 10-20% per year power loss of psu's, and b)42.6A
continuous can't be put out by a psu with a 40A continuous output. Some people just don't like admitting when they're wrong, even when it's quite obvious that they are.
have any link to this PSU power loss issue you bring up? i've never heard of it and that seems awfully high. take for example your PSU with 60A on the +12V rail... if it loses 10% per year (as seems to be your minimum power loss), then it would be down to about 44A after 3 years, which according to you means the OP's machine would suddenly not work any more... seems unlikely to me, esp. with a high quality PSU, but if you have proof, please link it.
and i have no problems admitting i'm wrong, but other than speculation, you haven't provided one shred of evidence to prove me wrong. i will gladly admit i'm wrong if you can explain what's wrong with this reasoning:
according to
anandtech, the MOST a single 8800gtx system (that's the WHOLE computer) uses under load is 301W. I did this analysis before: if we make the VERY CONSERVATIVE assumption that this is entirely from the GPU and is all over the +12V rail, that's 301W/12V = 25A. Using Howard's (conservative) estimate of 15A for an additional 8800GTX, that's a total of 40A.
So, with VERY conservative numbers, i get that a system with 8800GTX's in SLI will draw at the absolute most 40A, which means you'd want a 45A PSU to be on the safe side. realistically though, the system would use much less and you should (oh noes! i used the word should!) be fine with 40A or i would even GUESS (ah? what's that scary word mean?) 30-35A.
EDIT: again forgot to mention that these are minimums and if you look at the actual PSU's i recommended much earlier in the thread, i'm not actually advocating getting the bare minimum, but simply saying 60A is a gross overestimate.