[lm-sensors] [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR

Fenghua Yu fenghua.yu at intel.com
Tue Aug 31 23:01:13 CEST 2010


On Sun, Aug 29, 2010 at 06:42:36PM -0700, Huaxu Wan wrote:
> On Mon, 2010-07-26 at 11:16 +0300, Maxim Levitsky wrote:
> > On Sun, 2010-06-13 at 10:27 +0800, Wan, Huaxu wrote: 
> > > >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 
> > > >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 50C 
> > > >> > 
> > > >> > 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 
> > > >
> > > >
> > > >Any update? 
> > > 
> > > 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
> > > temperature.
> > > 
> > > 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. 

Hi, Maxim,

Could you send out thermal zone info under /proc/acpi/thermal_zone/TZ*?

Thanks.

-Fenghua




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