Making your G5 Chirp Scales

Probably most people who don’t own a G5 will have no clue what I’m talking about, and among those that do, a decent number will sigh when they hear mention of it. I’ve never gotten a full explanation on what the whole problem is, but when the power features for the G5 are enabled on a PowerMac G5 (as they are enabled by default), one will occasionally be greeted with noises like those described in this Apple support document.Well, up until now, this has just been a minor annoyance until I stumbled upon this lovely utility while looking around MacNN’s PowerBook/MBP forums. What does it do, you might ask? It can place variable loads on the processors found in your Mac. What’s so neat that the author of this app has discovered? Apparently, you can make your power supply play scales in the chirping noises. Here’s the explanation from the help docs included with SystemLoad:

the application tries to variate the load put on the processors in a certain pattern. This pattern is equivalent to the frequencies of a C-major scale between the notes C6 and C7. For processors consuming much power this causes the current (amperage) drawn by the processors to variate in the same pattern. For a dual CPU system with PPC 970 processors for example, the total current drawn by the processors will fluctuate between 22 and 120 amps in the millisecond range. Certain components in the power supply will start to ring with the same frequencies due to the high load changes. For some power supplies these changes become audible. Similar effects can be seen with the DC/DC boards of some PowerBook models.

Very random, but also very cool. Wonder if the author would put out an API for hooking this up as a MIDI output. You could play all kinds of interesting stuff :-)P.S.: I’ll give a try at recording this tomorrow. I don’t have any microphone around the house…

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