[chowells]

Long enough ago (win95 era) it wasn't part of Windows to sleep the CPU when there was no work to be done. It always assigned some task to the CPU. The system idle process was a way to do this that played nicely with all of the other process management systems. I don't remember when they finally added CPU power management. SP3? Win98? Win98SE? Eh, it was somewhere in there.

[drsopp]

I remember listening on FM radio to my 100MHz computer running FreeBSD, which sounded like calm rain, and to Windows 95, which sounded like a screaming monster.

[eggsome]

There were a number of hacks to deal with this. RAIN was very popular back in the day, but AMNHLTM appears to have better compatibility with modern CPUs.