Message-ID: <404CE0FC.8070900@stesmi.com>
Date: Mon, 08 Mar 2004 22:09:16 +0100
From: Stefan Smietanowski <stesmi@stesmi.com>
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To: Bjoern Schmidt <lucky21@uni-paderborn.de>
CC: linux-kernel@vger.kernel.org
Subject: Re: fsb of older cpu
References: <404C4D32.1080609@uni-paderborn.de> <200403081714.04182.bernd.schubert@pci.uni-heidelberg.de> <404CD4E7.5050105@uni-paderborn.de>
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>>> Hello,
>>> is there a way to measure/change the fsb of a PII/233/Tonga/440BX while
>>> running linux? Google has no answer...
>>
>>
>>
>> This is the only one I know about, but it has support for a few 
>> boards/pll's only.
>>
>> http://home.iprimus.com.au/mccvals/mvpll/
>>
>> Hope it helps,
>>     Bernd
> 
> 
> Hello and thank you for your answer. I determined that this cpu has a 
> fsb of
> 66MHz. The reason for my question was that i want to underclock the cpu.
> I think it would be better to change the multiplier instead of changing 
> the fsb.
> Therefore i read the msr register 0x02ah, tilted bit 27 and wrote it 
> back, but
> the cpu clock is still the same. Why does that not work? Is it possible to
> change the multiplier at runtime at all?
> 

I'm no expert on the subject but as I recall the processor sets the
internal clock (derived from fsb+multiplier) on startup so no matter
what you do do the running cpu it won't change it.

// Stefan
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