Motherboard blues

Friday, April 25th, 2008

Have you ever had a motherboard that works perfectly in some setups but mysteriously refuses to switch on in others? I ran into this problem during the testing for next month’s motherboards Labs. Surprisingly, it turns out the problem may be that your PSU is too powerful.

The explanation: ATX power supplies are designed to kick in when the motherboard starts demanding current. But there’s no industry standard for precisely how much current a board must try to draw before the PSU wakes up. Today’s hefty power supplies anticipate a heavy load, and if your motherboard asks only for a very small amount of power, it may fall under the threshold for that particular power supply.

There’s not a lot you can practically do about this – your options are, basically, to use a different PSU or a different board. I suppose in theory you could plug more things into the board to increase its power demands, but that’s not very green. Still, it’s all good stuff to know, and could save you a lot of frustrating trial and error should you ever run into the problem.

This tip was entrusted to me by a representative of a major motherboard manufacturer; and now I’m entrusting it to you. Guard it wisely.