[lm-sensors] [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR
huaxu.wan at intel.com
Sun Jun 13 04:27:17 CEST 2010
>On Wed, 2010-06-02 at 23:10 +0300, Maxim Levitsky wrote:
>> 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
>> > > > temperatures.
>> > > > First of all BIOS using stupid tricks actualy reports
>> > > > 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 , the TjMax(Tjunction) of T5450 is
>100C. Does anyone
>> > > here can make a double check?
>> > >
>> > > 
>> > This is very interesting.
>> > With TjMax 85C, the CPUs idle temperature is reported at
>> > GPU temperature that is around 50C
>> > BIOS also reports 45~50C.
>> > BIOS hooks an SMI to CPU thermal report, and stores the
>> > 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
I'm occupied by other things, sorry for slow response. But, as said in a
spec, I can't remember which one now, there are too many, the relative
value read from DTS is accurate approaching to TjMax. The accuracy
deteriorates to +-10C at 50C. Any DTS reading below 50C should be
considered to indicate only a temperature below 50C and not a specific
So, the value around 50C can't be taken as real chip temperature. I
would like this issue could be confirmed by more users to avoid it as a
particular case. At the meantime, I still looking for a laptop with T5450,
this may take some time.
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