What Power Supply?

[Milo]

Hiya,
What is the determining factor when spec'ing a power supply? I am seriously considering upgrading my PC from its current AMD Athlon based system to an AMD Phenom II X4 based system.
From all I've checked on the 'net, the only component that specifies a power supply is the graphics card, and as I'm interested in the Gainward Radeon HD4830, it spec'd a 450W P/S. Are there any other determining factors when choosing a P/S?
Bigger is not always better as it increases HEAT, and thus NOISE to cool the damn thing.

All thoughts appreciated,
Milo

[nevovx]

Full Load Efficiency, not all same wattage group P.S.U behave the same , for example pick 10 "750W" P.S.U models or brands and compare the full load efficiency you might see some draw upto 600W from the outlet and some of them around 400W full load all using the same pc components. You will usually see efficiency in percentage. Like 80% or 75% or 85%.

Stability; Components used in the power supply itself is an important factor for stability and performance of the pc itself. Power supply converts the voltage to required amount and vattage , e.g 12V rail , 5V rail , 3.3 v rail etc. Less fluctant changes and close the number as much as possible proves the stability of the power supply to continusly delivery the required amount. When the amount changes from idle to load thats where few cheap brands fails to delivery the required amount and thus causing crushes or damage to the component.

Although most branded power supplys looks same in price/wattage wise they do differ when it comes to proper testing.

You can look at the power supply tests by many computer websites and see these are the main two category they test power supply's. There are more deciding factors between power supplys which goes into more technical of course.

Check this link for a recent review and testing methodology

http://www.hardwaresecrets.com/article/522

[nstz]

I recommend the CORSAIR CMPSU-450VX 450W ATX12V V2.2 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Retail
Voted Best Power Supply Manufacturer by Custom PC 2008

It is quiet and very stable. When there are power glitches, other appliances and PC goes down, but not the computer with this.