linux-kernel - Re: Linux 2.6.25 (coretemp reads high temperatures)

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Message-ID: <20080502203615.GF3956@ucw.cz>
Date:	Fri, 2 May 2008 22:36:15 +0200
From:	Pavel Machek <pavel@....cz>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Kasper Sandberg <lkml@...anurb.dk>,
	Rudolf Marek <r.marek@...embler.cz>,
	Maxim Levitsky <maximlevitsky@...il.com>, trenn@...e.de,
	Len Brown <lenb@...nel.org>, Matthew <jackdachef@...il.com>,
	linux-acpi@...r.kernel.org, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, "Zhang, Rui" <rui.zhang@...el.com>
Subject: Re: Linux 2.6.25 (coretemp reads high temperatures)

Hi!

> > > So, im confused.. The reason for this is that the internal sensor is
> > > operating on some sort of weird scale, and thus when you interpolate it
> > > into "your" scale, it doesent quite come out in the actual degrees
> > > celcius the cpu temperature really is?
> > 
> > It's really only an offset, rather than scaling. The temperature
> > reported by the Core and Core2 CPUs is a relative temperature. It tells
> > how far you are from the maximum temperature the CPU can survive. The
> > value is expressed in (relative) degrees C.
> 
> Ah, please ignore my email about ITUs (Intel thermal units), then.  The
> above means 1ITU=1°C, but their zeros are at different places.
> 
> > Rudolf did his best to find out the (absolute) temperature each CPU
> > model can survive (known as TJmax) so that the coretemp driver can
> > provide an absolute temperature to user-space, as all other hardware
> > monitoring drivers do. Our hope was to limit the confusion, but it
> > seems we failed ;) Maybe it would be better if the driver was reporting
> > the relative temperature value directly when we don't know the TJmax
> > value for sure - but then all user-space tools would need to learn how
> > to deal with this.
> 
> Actually, just libsensors would, and the local admin can adjust it at
> will using the config file.
> 
> Nobody in userspace should be reading hwmon sysfs directly without the
> use of libsensors.  If they are, it is their bug, and it is unsupported
> AFAIK.

Hmm, that's an interesting ABI design. No, I do not think that's a
good idea.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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