linux-kernel - Re: Intel Core2Duo mobile - how does the VID get set?

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Message-ID: <47BB20F0.8030506@fenrir.org.uk>
Date:	Tue, 19 Feb 2008 18:33:20 +0000
From:	Brian Morrison <bdm@...rir.org.uk>
To:	linux-kernel@...r.kernel.org
Subject: Re: Intel Core2Duo mobile - how does the VID get set?

Pallipadi, Venkatesh wrote:

>> After a fair bit of Googling and reading around, I'm none the wiser 
>> about exactly how Linux 2.6.x sets the processor VID (or for 
>> that matter 
>> how it decides the FID settings) when using the ondemand governor and 
>> cpufreq stuff.
>>
>> Can anyone tell me a) whether this is obtained from the BIOS, 
>> something 
>> in the MSR of the processor or elsewhere and
> 
> Yes. The freq and voltage supported comes from the platform BIOS. BIOS
> exports this in an ACPI table which is handled by acpi-cpufreq driver in
> Linux kernel.
> 

OK, thanks for that.

>  
>> b) whether there is an 
>> interface in /proc or /sys where one can find out what is set 
>> and modify it?
> 
> There is no way of modifying and using new VIDs etc in Linux kernel
> (other than exporting your own DSDT and hacking the related code).

Is there a way of viewing the ACPI table contents relating to the VIDs
and FIDs?

-- 

Brian Morrison

bdm@...rir.org.uk

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