I have noticed a trend lately of computers making an annoying whining sound when they are running at low utilization. This happens with my Dual G5 PowerMac, the Dells I ordered 18 months ago for my staff (before we ditched Dell for HP due to the former’s refusal to sell desktops powered with AMD64 chips instead of the inferior Intel parts), and I am starting to notice it with my MacBook Pro when in a really quiet room.

These machines emit an incredibly annoying high-pitched whine when idling, one that disappears when you increase the CPU load (I usually run openssl speed on the Macs). Probably the fan falls in some oscillating pattern because no hysteresis was put into the speed control firmware. It looks like these machines were tested under full load, but not under light load, which just happens to be the most common situation for computers. The short-term work-around is to generate artificial load by running openssl in an infinite loop, or to use a distributed computing program like Folding@Home.

Load-testing is a good thing, but idle-testing is a good idea as well…