linux-kernel - Re: [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR

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Date:	Wed, 02 Jun 2010 19:34:16 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Huaxu Wan <huaxu.wan@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
	huaxu.wan@...el.com, khali@...ux-fr.org
Subject: Re: [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR

On Mon, 2010-05-31 at 09:39 +0800, Huaxu Wan wrote: 
> On 08:39 Sat 29 May, Maxim Levitsky wrote:
> > On Fri, 2010-05-07 at 17:59 +0800, Huaxu Wan wrote: 
> > > The MSR IA32_TEMPERATURE_TARGET contains the TjMax value in the newer
> > > processers.
> > 
> > I know that TjMax on my system is 85, and now coretemp reports wrong
> > temperatures.
> > First of all BIOS using stupid tricks actualy reports CPU temperature
> > through ACPI, and assuming it was correct TjMax is 85.
> > It also shuts down the system if I 'lie' to it that cpu temperature is
> > 85C.
> 
> From the list at [1], the TjMax(Tjunction) of T5450 is 100C. Does anyone
> here can make a double check?
> 
> [1] http://ark.intel.com/Product.aspx?id=30787&processor=T5450&spec-codes=SLA4F

This is very interesting.

With TjMax 85C, the CPUs idle temperature is reported at around 45~50C
GPU temperature that is around 60C

BIOS also reports 45~50C.

BIOS hooks an SMI to CPU thermal report, and stores the temperature it
read in ram, then ACPI code reads it, reports and passes to the EC
(embedded controller).

If I write myself 85 to embedded controller, systems shuts down.
(values less that 85, eg 84 don't shut system).

Thats all I know.

Best regards,
Maxim Levitsky

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