nforce2 cpufreq

[Nate Lawson]

Andriy Gapon wrote:
> I've recently had a sudden urge to investigate power saving / cpu
> throttling options for my desktop Athlon XP system.
> It seems that the CPU itself does not provide any interfaces for that,
> at least neither of acpi_perf/acpi_throttle/cpufreq seem to detect
> anything interesting for them.
> Or am I mistaken and doing something wrong ?
> 
> Anyway, my MB is based on nForce2 chipset and I found out that Linux has
>  cpufreq-nforce2 module that works in their cpufreq framework:
> http://www.hasw.net/linux/
> 
> It seems that that module works by using nForce2 PCI interface for
> querying and changing FSB frequency. It also seems that the code is
> rather simple and obvious in its logic (save for allegedly
> reverse-engineered constants). Not sure though how easy it is to port
> that to FreeBSD cpufreq framework.
> But the question that I really would like to ask is the following: is it
> a proper way to do cpufreq stuff by changing FSB frequency ? Would that
> approach fit into our framework ? And finally, would it have any
> positive temperature/power consumption effects ?
> 

It's really easy to do.  Just see the sys/dev/cpufreq/ichss.c file.

-- 
Nate