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

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Date:	Mon, 26 Jul 2010 11:16:28 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	"Wan, Huaxu" <huaxu.wan@...el.com>
Cc:	'Huaxu Wan' <huaxu.wan@...ux.intel.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'lm-sensors@...sensors.org'" <lm-sensors@...sensors.org>,
	"'khali@...ux-fr.org'" <khali@...ux-fr.org>
Subject: RE: [PATCH 2/2] hwmon: (coretemp) Get TjMax value from MSR

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. 
> 
> Thanks
> Huaxu 

Any update?

Best regards,
Maxim Levitsky

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