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Choosing a PSU.


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#1
iman7

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How exactly do you select the right PSU for a computer? I'm not really acquainted with the +12v rails and such other terminologies. Although I do know what certain power connectors are and what they are used for, but that's as far as it goes.

I do not understand exactly what the 12v rails are, how they are used when it comes to PC power. And I want to know because I am upgrading to the HD 3850. Since my current PSU is only 550 watts with 20amps on a single 12v rail according to the sticker on the side.

Edited by iman7, 12 January 2009 - 07:45 AM.

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#2
Webslinger64

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How exactly do you select the right PSU for a computer? I'm not really acquainted with the +12v rails and such other terminologies. Although I do know what certain power connectors are and what they are used for, but that's as far as it goes.

I do not understand exactly what the 12v rails are, how they are used when it comes to PC power. And I want to know because I am upgrading to the HD 3850. Since my current PSU is only 550 watts with 20amps on a single 12v rail according to the sticker on the side.


Good question, and to add one more to the mix just cause I don't know...Can you have a PSU that puts out too much power for the mobo, CPU and other hardware that you have installed? As an example, I have a Pentium 4, 1.8GHz, 2GB RAM, GeForce 6600, Sound Blaster and a 300 Watt PSU. I've been thinking up upgrading my PSU and found one in a local classified ad for sale (brand new, just never used) and it's 750 Watt. Could that be too much for me?
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#3
jrm20

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How exactly do you select the right PSU for a computer? I'm not really acquainted with the +12v rails and such other terminologies. Although I do know what certain power connectors are and what they are used for, but that's as far as it goes.

I do not understand exactly what the 12v rails are, how they are used when it comes to PC power. And I want to know because I am upgrading to the HD 3850. Since my current PSU is only 550 watts with 20amps on a single 12v rail according to the sticker on the side.


Good question, and to add one more to the mix just cause I don't know...Can you have a PSU that puts out too much power for the mobo, CPU and other hardware that you have installed? As an example, I have a Pentium 4, 1.8GHz, 2GB RAM, GeForce 6600, Sound Blaster and a 300 Watt PSU. I've been thinking up upgrading my PSU and found one in a local classified ad for sale (brand new, just never used) and it's 750 Watt. Could that be too much for me?



You want to find a good quality brand that does not use cheap internals and DO NOT buy a CHEAP psu for $25 as an example. Look for the 12 volt rails to have high amps. 18 amps or above is a good PSU (ON a quality brand) if it has multiple 12 volt rails. Some brands such as Pc Power & Cooling may only have one HUGE rail with 60 amps for example which is a good choice also.


As for the PSU, your computer only uses or draws the amount it needs from the power supply. You can have a 1000watt psu on a low end build if you wanted to as an example but there is no reason to. So your answer is NO it cannot supply to much power..
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#4
iman7

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Amperage on a dual rail PSU isn't really cumulative right? Even if they total to more than 30 Amps combined, the other rail would more or less be useless, right?

I'm having trouble finding a PSU for a MSI K9A2 Platinum from my local dealer. I don't know if buying a PSU with two rails would hurt a system running on one or let it work all. But it probably will hurt it with the reduced amps.

Here's a link to their PSU list.

And all the single rail Antec one's are less than 500watts.
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#5
Troy

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http://www.pcbodega....php?c=69&p=7997
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#6
TM_Skylark

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It has been shown that purchasing a PSU with one rail is more energy efficient than purchasing one with multiple rails - having more than one rail is to an extent a marketing gimmick.

That said, use Antec's Power Supply Calculator in order to give you a general idea of how much power you need.

I always add a 100W buffer because power supplies do degrade over time.

Next, only purchase a PSU made by the following companies. In the PSU industry, name DOES matter: Antec, Channel Well, Corsair, Enermax, Enlight, Fortron Source, OCZ, PC Power & Cooling, Seasonic, Sparklepower, Thermaltake.
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