Power Supply Selection.

Can anyone explain to me, in 5 words or less , why the size of a power sypply, as in DC Wattage Output, is so important.

Why I ask is that my PC has a 250W Power Supply, and it works fine, yet on a TV Program I was watching, the Moderator insisted that the absolute minimum should be 300W, and that 400W was even better.

Many Thanks.

 

Your PC will work fine with the PS that came with it.

The problems start when you start adding more gear such as HDD's, CD drives, More ram, bigger CPU, Video cards and the like.

In other words, the more you use, the more you need.

 

For example, I tried using an Enlight 300W PSU in a rig with 3 hard drives and a CD-Rom and it wouldn't boot unless I disconnected at least one of the hard drives.

I put in another PSU (this was actually 300W too but a much better quality PSU - Seventeam) and it booted with all drives attached.

Sometimes its not just the wattage rating but the quality of the PSU that counts as well. If you're building a rig from scratch, anything less than 350W is a waste of time and money.

Stick with Antec TruPower PSUs (380W, 430W) and "don't worry, be happy! ".

 

Thank you for the replies.

I guess I just figured that, in general, a PC could only use one drive at a time and therefore the rating of the power supply was irrelevant.

As to items such as the RAM, I did not think that this should even be a factor, but obviously I was wrong.

Once more this BBS has come through.

 

Wattage is measured in amperage times volts. Each peripheral/component on the circuit draws "X" amps and is additive. With max. watts and volts fixed, amperage's outside parameter is limited to the watts of the P/S.

One can almost never have to much power, but there is always a risk of not enough ( also line voltage may fluctuate). Your reasoning of one component/peripheral at a time is not without merit. Control is turned over to different peripherals/components on an interrupt bases and integrated into the overall system pertformance. So not all components are drawing or drawing down equally at any given time.