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PSU recomendations. PSU Calculators misleading.

Last response: in Components
July 14, 2009 2:08:35 PM


I don't know if I need to electrician to be able choose a good PSU , with all the letters and number together +12V -12v 18A .. All this only reminds me of Intergral calculas. I don't understand it and as far as my GPU goes , it recommends a 450w Power supply but when I use eXtreme power calculator I came upto only 268 W . Now I'm confused.

The build includes
AMD Athlon 7750(2.7ghz)
ATI Radeon 4850
DVD/CD RW combo
Corsair XMS2 800mhz

Will a 350 watt Corsair do for all this and overclocking the 7750 to 3 ghz? . Is Corsair the best in PSU?

July 14, 2009 2:54:30 PM

Corsair is one of the best brands. Specify the 12V wattage output of the Corsair and I'll give a definite answer as to whether the PSU can handle your specs.
a c 144 ) Power supply
July 14, 2009 4:50:42 PM

I checked newegg. The smallest Corsair they have is a 400 watt unit:

It has a 30 amp 12 volt rail. That is certainly good enough. Figure that a 350 watt Corsair would have about a 25 amp 12 volt output. That's a little close for my taste.

My SWAG (scientific wild assed guess) for your power consumption:

CPU - OC'd: 8 amps @ 12 volts = 96 watts
GPU - 9 amps @ 12 volts = 108 watts
HD - figure 1 amp at 5 volts & 1 amp at 12 volts (labels will say a little less) = 17 watts
DVD - 1.5 amps @ 5 volt & 2amps @ 12 volts = 30 watts
2GB RAM - 3 amps @ 3.3 volts = 10 watts
MB - 3 amps @ 5 volts & 1 amp @ 12 volts = 27 watts
Fans - 1 amp at 12 volts = 12 watts

I get about 280 watts. Keeping in mind that I rounded upward in a couple of places, the eXtreme power calculator pretty closely agrees with me. :bounce: 

Video card manufacturers always overestimate power needs. For one reason, they cannot assume that you are going to select a good PSU. They have to assume that some people are going to select something like the Rosewill's.

I prefer to operate my power supplies at between 50% and 70% capacity. Your system would load a 350 watt PSU at about 80% of capacity. That's well within specs and the specified 80% efficiency, but as I said, I would prefer a 400 - 450 watt PSU.

And, yes, Corsairs are top bracket PSU's throughout the whole line.
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a b ) Power supply
July 14, 2009 5:12:31 PM

hash said:
Will a 350 watt Corsair do for all this and overclocking the 7750 to 3 ghz? . Is Corsair the best in PSU?

Corsair is very good, but they don't make a 350W.
July 15, 2009 2:03:47 PM

thanks a lot for the info. I'll go for a Corsair 400.