Subject: Re: MP, SP, extintr, mc, ofb
To: Dan LaBell <dan4l-nospam@verizon.net>
From: Michael <macallan18@earthlink.net>
List: port-macppc
Date: 12/15/2004 06:03:47
Hello,

> I've been wanting to post about this for a while,  I've noticed that if 
> I boot my ibook into OSX after using Netbsd, the fan always kicks in, 
> and runs for a few minutes, it also does this after prolonged sessions 
> in openfirmware.  One time, I was trying to make bootmenu in OF forth 
> and spent maybe over an hour in OF, at which time it got kind of 
> flakey, as if keys were sticking -- I booted in OSX to let it cool 
> down, and the fan ran for about 20 minutes...
> Typically the fan never comes on, in OSX, unless I make heavy use of 
> the cdrom.
That has a simple reason - the fan controller works autonomously. That's why the fan spins up and down at all While NetBSD is running. But OF programs rather high temperature values for the fan(s) to spin up, MacOS X apparently changes them to lower ones, so the iBook will run pretty hot in OF and NetBSD but remain cool in OSX. As soon as I figured out how to (ab)use sysctl to talk to my driver NetBSD will be able to change these things too, at least for those models using the same controller ( an Analog Devices ADT 7467, see the 'compatibility' property of /uni-n/i2c/fan in OF )

> Netbsd-wise, I'm a little concerned if OSX feels the machine is hot 
> enough for some fan, unless its something else, like OSX sees different 
> values in fan related registers/varibles than it uses, and just 
> defaults to running the fan for a few secs..
Hmm, the controller has 'calibration registers' to compensate linear errors in temperature measurement, but I left them alone and the readings looked rather high.

have fun
Michael