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

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Date:	Wed, 02 Jun 2010 23:10:16 +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 Wed, 2010-06-02 at 19:34 +0300, Maxim Levitsky wrote: 
> 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).


Another clue is that right after resume from ram, after long delay
(~hour) the displayed temperature with TjMax 85 is 33C. Since room
temperature here is around 27C, this seems more plausible that 
33 + 15 = 48C 


Best regards,
Maxim Levitsky

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