Sign in with
Sign up | Sign in
Your question

How to read PSU specs

Last response: in Components
Share
May 4, 2005 10:37:45 AM

Can anyone explain, or at least point to where I can gleam information, on what exactly the PSU specs mean. I'm referring to these specs, specifically the meaning and significance of the voltage and amperage listings:

<A HREF="http://images10.newegg.com/productimage/11-170-019-12.J..." target="_new">Kingwin PSU specs (as an example)</A>


Thanks!


Mad Cat

More about : read psu specs

May 5, 2005 7:45:12 AM

They mean almost nothing. Other people will say differently. But you have to read reviews from trusted sites who actually test the full output power in order to know how accurate those numbers are.

Watts are simple math, amps times volts. 12 amps times 12 volts equals 144 watts, for example. But you might find a cheap power supply that claims 30A on the 12v rail and is only capable of 28A, and starts dropping voltage at 20A, which means for all intents and purposes it's only a 20A rail. It's the things they don't tell you that make the difference.

Another thing they don't tell you is, how many capacitors are inside, how many filter coils, or how good those parts are. I repair power supplies that have died within a few weaks at 1/2 their rating.

And one more thing, a power supply with poor filtration can make your entire system unstable. Of course, you can help a cheap power supply allong by putting it behind an expensive Uniteruptable Power Supply.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
May 5, 2005 4:55:02 PM

In addition to what Crash offered... a huge cardinal sin (deceptive practice) most manufacturers make is testing their PSU's at 25c (about 55f) and claiming that full rated output at normal operating temps (40-45c). Generally the hotter the PSU gets the more the actual true power output drops. The average 550w PSU will actually output something in the neighborhood of 350-375w at normal operating temp (40-45c). And at commercial grade temps (50c), it drops further to around 250w. But the manufacturer of your average 500w $50 "Special" with the transparent UV blue case and 2 80mm blue LED fans will never disclose these details on their label nevermind the packaging. So once you understand how derating works, you get a better idea of which manufacturers to stay away from.

"The world ends when you're dead. As long as your breathing you got more punishment in store. Stand it like a man and give some back."
May 6, 2005 5:10:50 AM

Eh, sorry, for some reason it posted the wrong thread for this response.


<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
!