Fan control for PowerMac7_3 (#3)

[Benjamin Herrenschmidt]

On Sat, 2004-10-16 at 15:32, H. Peter Anvin wrote:

> It's the backside fan that oscillates; backside_fan_pwm varies between 
> 30 and 100 in what is pretty much a squarewave.  See attached graph (and 
> note how the other fans vary with workload.)
> 
> I probably need to write a "power virus" program for the G5 to really 
> test out the high end (a power virus is a program which keeps the chip 
> running as hard as it can; generally keep all pipelines stuffed.)

Strange... The values used seem to be identical to OS X (a 75° target
which is high actually, and a different G_d value than old U3). I would
need to see the debug output and compare with the OS X driver built with
debug output as well (don't ask me to fully understand the math of the
PID algorithm)

Ben.