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GTX 460 with 20A rails. Is it enough?

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August 20, 2010 7:39:26 PM

I recently purchased a 950W Rosewill PSU during a Newegg shellshocker. I got it for \$57 + tax so it was damn cheap. I am in the process of buying components for a new gaming rig and figured it would be good enough to run a couple GTX 460 in SLI.

Upon further investigation I found that it only has 20A on each of it's four 12V rails. I have read up on it since and found that at least a couple GTX 460 cards are recommending a minimum of 24A for these cards.

Is there anyone who has tried running a GTX 460 with only 20A available?

And/or, can I run a power connector from two separate rails since it requires two power connectors? Or is that going to cause some issues?

If I have to buy another PSU I will, but I am just trying to figure out what my options are.

Thanks in advance for any input.

More about : gtx 460 20a rails

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a c 276 ) Power supply
August 20, 2010 7:42:48 PM

Its not the power on the individual rail that matters, its the combined power between the rails since the power ratings on the cards are for the system as a whole and the CPU and motherboard are almost always on different rails from the PCI-E connectors, it will have more than enough power for a GTX460 or even 3 of them.
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a b ) Power supply
August 20, 2010 10:43:48 PM

20amps x 4 = 80 amps! more than enough!
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a c 243 ) Power supply
August 20, 2010 10:48:12 PM

iam2thecrowe said:
20amps x 4 = 80 amps! more than enough!

Ah, if only it actually worked that way.
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a c 276 ) Power supply
August 20, 2010 10:48:53 PM

iam2thecrowe said:
20amps x 4 = 80 amps! more than enough!

WRONG! 4 rails with 20A each rarely equals 80A, very few times is the total power actually the addition of the power of all the rails, in the case of the 950W rosewill PSUs, he has 67.5A between the 12V rails NOT 80A like normal math would lead you to believe.

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a b ) Power supply
August 21, 2010 2:10:07 PM

It's always best to subtract the other voltages from the total and the remaining is the +12V.
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a c 276 ) Power supply
August 21, 2010 2:23:08 PM

Not for the DC-DC conversion PSUs where all of the other rails are converted off of the 12V rail and since you are very unlikely to load up the 3.3V and 5V rails to their rating on the power supply your actual available 12V power will be much higher than that math would lead you to believe, which is why i never try to do any math, i just look at the load table for a combined power rating for the 12V rail.
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a b ) Power supply
August 21, 2010 2:31:01 PM

Didn't know that, thanks. But when there's no such table? For instance all you know is this (FSP SAGA 500W):

+3.3V@22A, +5V@16A, +12V1@14A, +12V2@16A, -12V@0.8A, +5VSB@2.5A
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August 21, 2010 9:45:58 PM