Power supplies are the only part of the computer that I know nothing about. I don't know what the forget rails are, I don't get why a 500w power supply might not run something that uses 10 watts, and I don't get anything about them :D
I do know how to short them out to make them run without having to be connected to the motherboard, though.
A lesson in Power Supplys from Reactor WorkerWhen choosing a power supply, or determining whether your current one is adequate, there are 2 important factors to consider...
1) Amperage
2) Wattage
Generally a chipset maker (Like Nvidia or ATI) will specify the power requirements of a GPU. I have listed an example from the EVGA website below....
9600GT models
Minimum of a 400 Watt power supply
(minimum +12 Volt current rating of 26 amps)
An available 6 pin PCI-E power connector
It's always best to exceed the minimum requirements, but not necessary.
As stated above, in order to use the 9600GT you need a 400 watt PSU. This is based on the needs of the card + an estimate of the power needs of the other components in your system (such as the CPU, HDD's etc).
The tricky part is the +12 volt rails. Some PSU's have 1 rail, others have multiple ones. For a single rail, the answer is easy. Check the specifications and see what amperage it states. Usually it will say something like...
+3.3V@30A, +5V30A, +12V@40A, -12V@0.8A, +5VSB@3.5A
The bolded words is the important part. That tells you that the +12V rail supplies 40amps of power.
For multiple +12v rails you need to check which connectors go where.
In most cases you can just add up the amperage's of all the +12v rails but it can change.
I personally prefer the Corsair Brand. They offer some of the highest quality PSU's and most of the time avoid all the multiple rail nonsense. When buying a powersupply, never cheap out. Stick the the quality brands and if it sounds too good to be true, it probably is. A higher quality 400 watt powersupply will outperform a cheap 600 watt powersupply.
