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Old 04-06-2011, 09:06 PM
 
11,715 posts, read 40,385,082 times
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A video card says it requires a 400w power supply capable of supplying 22A @ 12V. But it doesn't say whether all that current has to be on one rail. Even the more expensive brand name dual rail 400w power supplies supply about 17A per rail. The most I could find was 20A x 2 and even the $125 FSP CrossFire Ready unit only supplies 14A+13A.

So 22A on one rail doesn't seem to be within the capability of a 400w PSU. Since the card maker doeesn't say anything about 12V rails, does that imply that the stated amperage requirement is for the combined 12V output?
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Old 04-07-2011, 08:50 AM
 
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Quote:
Originally Posted by EscapeCalifornia View Post
A video card says it requires a 400w power supply capable of supplying 22A @ 12V. But it doesn't say whether all that current has to be on one rail. Even the more expensive brand name dual rail 400w power supplies supply about 17A per rail. The most I could find was 20A x 2 and even the $125 FSP CrossFire Ready unit only supplies 14A+13A.

So 22A on one rail doesn't seem to be within the capability of a 400w PSU. Since the card maker doeesn't say anything about 12V rails, does that imply that the stated amperage requirement is for the combined 12V output?
Yes, it needs a total of 22A combined across the rails. You simply add up the total amperage across the 12V rails to make sure you're covered.

So, your first example is 34 (17A * 2 rails).

The second is 40 (20A * 2 rails).

The third is 27 (14A + 13A).

Pretty much all the vid card manufacturers will state that you need a minimum of 22A across the 12V rails.
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Old 04-07-2011, 01:43 PM
 
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Old 04-08-2011, 08:31 AM
 
Location: Austin Texas
474 posts, read 903,453 times
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This article from Antec provides an interesting view on current and rails.

Antec power supplies are generally highly respected; some of them are OEM'd from Seasonic.
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