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Subject: Re: [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR
From: Maxim Levitsky <maximlevitsky@gmail.com>
To: Huaxu Wan <huaxu.wan@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, lm-sensors@lm-sensors.org,
       huaxu.wan@intel.com, khali@linux-fr.org
In-Reply-To: <20100531013950.GA8265@owl>
References: <20100507095945.GB12190@owl>
	 <1275111551.3427.4.camel@maxim-laptop>  <20100531013950.GA8265@owl>
Content-Type: text/plain; charset="UTF-8"
Date: Wed, 02 Jun 2010 19:34:16 +0300
Message-ID: <1275496456.32562.4.camel@maxim-laptop>
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Sender: linux-kernel-owner@vger.kernel.org
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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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