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ATX Motherboard and Power Supply

T

Tycho987

Junior Member
Hello everyone, I'm new to this forum.

I have a question about ATX style motherboards and power supplies.

I understand that when the computer is shut off, the motherboard runs hot (power is still being supplied), but exactly how does the power supply react (lets assume its rated at 300 watts)?

Does it convert 300 watts no matter what? In essence this would be wasting alot of power. A book I was reading on this wasn't exactly clear on this subject.

Thank you in advance for your help,

Dr. Microchip's Assistant


 
A 300 watt PWS just has a rated output of 300 watts. That does not mean that it is always outputing 300 watts. All tranformers do pull some power even when off, but that is probably less than a watt or so.

Also, just beacuse a PWS is rated for 300 does not mean that 300 is it's max. Also remember that the 300 is split between the different "rails" 3.3v 5v 12v ect. that is a TOTAL output that the PWS can handle. most have a 120-150 watt rating on the 3.3-5v combo, as that is where the CPU pulls it's power.

A 300 watt PWS only puts out 300 watts as well. It will pull more than that from the wall, as it will loose some in the conversion process. That is what all those heatsinks are for. At full output, the PWS will probably be pulling about 330 watts. Assuming a 90% efficency.
 
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