Re: Make overclock possible with cpufreq

[Dave Jones <davej@redhat.com>]

On Sun, May 28, 2006 at 10:26:56PM +0200, Matteo Giordano wrote:

 > I just subscribed to the list to address this issue (I think it's an 
 > *issue*).
 > I'm not a kernel hacker so I'm just guessing here, even if I searched
 > and tried all the afternoon.
 > It's not possible to use cpufreq with an overclocked CPU because the
 > processor's frequencies are "hardcoded" somewhere (the BIOS or a PSB
 > table?).
 > So if I push my Athlon 64 3200+ to 2.4GHz the "performance" governor
 > will always put it to 2GHz max, causing the overclock to be useless.
 > 
 > Isn't really possible to take the _actual_ frequencies into cpufreq?

It's reliant upon the BIOS tables describing valid frequency/voltage pairs.
Obviously, your BIOS has no knowledge of overclocked values.

There's nothing sane we can do here. The only possible way this could
work would be by having a mechanism to feed such pairs to the driver,
overriding the BIOS.

Patches to do this have been posted to the list in the past, but I'm
not enthusiastic about applying them to the mainline kernel, as the
potential for getting something wrong if you don't know what you're
doing is huge, and this has the possibility of exposing hard-to-track
down bugs.

		Dave

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