Slayer wrote:
but the wattage between the wall and PSU should be 110 or 220 depending on what its set at shouldnt it (The switch on the back of the PSU)
Disposable wrote:
The 100/220 figures you mention are the Voltage specs not the Wattage specs.
Yes, that's the voltage of the electricity that is delivered to your home by the power company. Depending on what country you live in determines whether you get served electricity at 100/110V or 220/240/250V. That switch is for changing the PSU between different regions (on older PSUs, most new ones nowadays have circuitry that does it automatically, so they no longer have a switch).
BTW, that switch is sometimes known as the self-destruct switch because if you set it to 110V when your electricity supply is 240V, for example, it will blow up the PSU.
Watts (power) = Volts (electric potential) * Amps (electric current)
The PSU's job is to convert the voltage from your wall socket to levels of 12V, 5V and 3.3V that the PC components actually run off. I mentioned before that the sticker on your PSU will list the amperage it delivers for each of the different voltages. If it does for example 20A for 12V, then it is capable of delivering 12 * 20 = 240W to the components that run off the 12V electricity. The total wattage value of the PSU is usually given as the sum of these wattages, however, because it is cheaper and more economical to share the circuitry that does this (as opposed to having independent circuitry), the load on one line will actually affect the output of the others (this is another grey area in PSU ratings).