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Power supply and gtx480 sli problem

Last response: in Graphics & Displays
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August 12, 2012 7:24:17 AM

Hi, i have a little problem...

The psu i got is a CM Silent Pro 1000w / 80A . I thought it was enough to power my gtx480 SLi, but the power that goes on the 12v rail is 963w which is enough for the setup BUT if I want to overclock the gpu's.....It seems it is not enough. I bumped the voltage from 1050mv to 1138mv to attain 900mhz core and Windows automatically restored default settings.. Afterwards, I decreased to 850core 1125mv....was stable for a longer time but failed at the end. I Also get those random GPU Core downclock when playing: seems my video cards are downclocking to prevent any power issue ( i did modify the power mangement mode in NV control panel to see if anything changes, but in vain). I'm assuming the cards require more power. Btw, every component is very well cooled. The gfx's don't exceed 70C.

I would like to have your opinions, maybe i'm completely wrong... So What do you think? What seems to be the problem?

specs :

amd phenom II x4 965 BE oc'd @ 4ghz
8gb ddr3 gskill ram 1333mhz
gtx 480 SLi
nf750-g55 mobo
cooler master m1000

a c 185 U Graphics card
a c 122 ) Power supply
August 12, 2012 8:33:10 AM

For a system using two GeForce GTX 480 graphics cards in 2-way SLI mode NVIDIA specifies a minimum of a 900 Watt or greater power supply that has a combined +12 Volt continuous current rating of 67 Amps or greater and that has at least two 6-pin and two 8-pin PCI Express supplementary power connectors.

Total power supply wattage is not the crucial factor in power supply selection. Total continuous amperage available on the +12V Rail(s) is the most important.Please don't be insulted it seems like you know this already so it's more of a making sure thing than anything personally i think when your overclocking those beasts it's pushing your psu past what it can honestly handle my friend has 480's in sli he tested it before at stock clocks he told me his pair of GTX 480s draw 864W. When overclocked, he seen them draw dam near 1000W. However this is just hear say i didn't actually see this but maybe it's true.So if you don't overclock, you have enough. I am pretty shocked that your not getting bottle necks with the cpu you have but other than that i have no clue
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August 12, 2012 8:56:42 AM

i do have a bottleneck, how great is it? quite big....a delta of 200mhz on the cpu clock speed can vary fps of about 2-6 during gaming. I have my cpu clocked at 4ghz meaning i gain around 6-18fps from the original clock speed... Obviously im approximating, could be +/- 10%.
Anyways, if what bigcyco1 says is true about the wattage for 2way sli gtx480, then i know the problem...The psu i have has a rated amperage of 80A which is plenty enough. The wattage, on the other hand, is in short. Man, shouldve bought a watercooled gtx670 instead of 2 gtx480...

Please if you have any other ideas of what could the problem be, i would greatly appreciate it if you share.

thanks
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a c 185 U Graphics card
a c 122 ) Power supply
August 12, 2012 9:20:24 AM

lol i try it another way with corsair utility though it's not 100% reliable i found it funny what it said Your system is an absolute monster! With this kind of hardware, you need an absolute beast of a power supply. Luckily, Corsair has that taken care of. Click below for more information.
http://www2.corsair.com/psufinder/go.aspx?psu=Professio...

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