From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rudolf Marek Subject: Re: Linux 2.6.25 (coretemp reads high temperatures) Date: Wed, 30 Apr 2008 00:14:12 +0200 Message-ID: <48179DB4.8040701@assembler.cz> References: <200804182151.49021.lenb@kernel.org> <200804231143.10875.maximlevitsky@gmail.com> <1209406784.11608.15.camel@localhost> <1209474423.1784.837.camel@queen.suse.de> <20080429170824.09540206@hyperion.delvare> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20080429170824.09540206@hyperion.delvare> Sender: linux-kernel-owner@vger.kernel.org To: Jean Delvare , Maxim Levitsky Cc: trenn@suse.de, Kasper Sandberg , Len Brown , Matthew , linux-acpi@vger.kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, "Zhang, Rui" List-Id: linux-acpi@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi all, I already answered this thread while ago. I can just confirm what Jean = told. >>>> I confirm this. >>>> I *know* that temperatures reported now are wrong. >=20 > And how do you know? The newly reported temperatures could be correct > and the previous ones were incorrect (that's actually the case.) The > thing is, the temperature is stored as a relative value in the CPU. > Relative to what, depends on the CPU model, can be 85=B0C or 100=B0C.= Up to > kernel 2.6.24 we had a set of rules to find out, in 2.6.25 we have a > presumably better heuristic. So some people have seen their CPU > temperature climb by 15=B0C and others drop by 15=B0C, that's expecte= d. Yes exactly. I decided to move to 0-100C scale, and move the limit too. Of course some users with too low jumped to better scale some like you = seems to complain now. >>> i have watercooling, and well :P when i touch the "tube", its norma= l >>> room temperature, and believe me, i would notice if it was 45.. thi= s is >>> with my cpu at idle - at full load on all 4 cores, temp2 says 35, a= nd >>> ~60 on coretemp, and THIS i would surely be able to notice over roo= m >>> temp :) >=20 > The coretemp driver reports the CPU _core_ temperature. That's not > something you can touch, believe me (unless you are an electron.) >=20 > Also note that the CPU temperature reported by the IT8718F may or may > not match the reality. To make sure, you'd need to know the type of > thermal diode expected by the IT8718F, the type of thermal diode in > your CPU, compute the correction factor if there is one. And you'd ne= ed > to know where the thermal diode is exactly. It is most certainly buil= t > into the CPU, but some motherboard makers are doing weird things. >=20 > 22=B0C seems very low to me, even for water-cooling. Note that > non-linearity of thermal diodes makes measurements inaccurate as they > get away from the expected operating point. I guess that thermal diod= es > used in CPUs are calibrated for best results around the expected > temperature when using air-cooling, rather than water-cooling. >=20 >>> any progress on this bug? >=20 > I still need to be convinced that there is a bug here. It is not a bug, a max limit changed too, it is just matter how to scal= e it. The temperature is non-physical so comparing it to physical temperature doe= s not make any sense. I'm sorry I did not invent this relative temp stuff - C= omplain @intel. They have some calibration of TjMAX for mobiles, but this bit d= oes not work for desktops/servers. I tried really hard to get at LEAST some documentation so the driver looks like it looks. And not guessed/guessed/guessed/how it looked earlier. >=20 >>>> The reason is that bios did report same temperatures as coretemp i= n 2.6.24, >>>> moreover some time ago I have run a cpu tool (don't remember its n= ame) on windows It was most likely coretemp - I'm in contact with the guy. We share inf= os. >>>> temperature of both cores >>>> (I had to run this on windows - intel haven't released=20 >>>> drivers for their QST for temperature monitoring from bios - very = sad) >>>> >>>> And the driver did say in kernel log that TJMAX is 85C >=20 > Which driver, which kernel? As I wrote above, the coretemp heuristic > changed in kernel 2.6.25, so the fact that a previous kernel was > reporting a different tjmax value is irrelevant. Unless you have > additional documentation from Intel, I would tend to believe that the > coretemp driver in 2.6.25 is correct. But feel free to report the exa= ct > CPU model you have (with CPUID info) to Rudolf, if he gets enough > reports about a specific CPU model which most people believe gets the > wrong tjmax, he can fix the driver. Well again, I tried hard at Intel and I really could not get any info o= n some calibration bit. The temperature is non-physical on arbitrary scale. I = changed that so for some people it jumped to 100C, for some it remained. >>>> Lets at least make a kernel option to override tjmax? >=20 > That's a possibility for sure, but what we would really need is to > adjust the coretemp driver heuristics to always get it right - if > that's not already the case, that is. I'll let Rudolf decide anyway. Well again, Intel swears there is no way how to get the TjMAX for desktops/servers. It sucks but this is not my fault. Thanks, Rudolf -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIF5203J9wPJqZRNURAnFSAKC3GpafvkviWggGJPG2o71R4lel0wCgirnW Cr2RidnTZEdKTAj8yEviR0U=3D =3DlFMk -----END PGP SIGNATURE-----