From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Rickman Date: Tue, 11 Jan 2011 08:47:45 +0000 Subject: [lm-sensors] Accuracy of "via_cputemp" Module in LM_Sensors Message-Id: <4D2C1931.5000301@myamigos.us> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: lm-sensors@vger.kernel.org Hi all, I am trying to track down a temperature discrepancy on a Jetway=20 J7F4K1G5D "Versa" motherboard. This board has a VIA C-7 D cpu (25W=20 version). The operating system is Fedora Core 14 i386, kernel=20 2.6.35.10-74.fc14.i686.PAE. I am running this version of "sensors":=20 sensors version 3.2.0 with libsensors version 3.2.0 LM_Sensors loads the following modules: acpitz-virtual-0 f71805f-isa-0290 (using acpi_enforce_resources=3Dlax) via_cputemp-isa-0000 I understand the risk of using "lax", but there is no ACPI version of=20 the "f71805f" module and Jetway ACPI grabs 0x295-0x296 from the IO range=20 0x290-0x297. Back to my question.... When I boot this machine I can read the System and CPU temperatures from=20 the boot screen. I can also go into the BIOS and read the same values in=20 the "PC Health" screen as seen on the boot screen. The boot values=20 typically show as 12C-16C for CPU temp and 27C-30C for System temp.=20 Others have posted comments elsewhere saying this VIA CPU does not run=20 warm, especially when idle, but that temperature range is approximately=20 the ambient range for the room where that machine is located. I thought=20 pushing electrons through silicon generated some heat? Once FC14 is booted, I can run the "sensors" command and see the=20 following values: [root@XX ~]# sensors acpitz-virtual-0 Adapter: Virtual device temp1: +11.0=B0C (crit =3D +60.0=B0C) f71805f-isa-0290 Adapter: ISA adapter [...voltages and fan info removed...] System Temp: +11.0=B0C (high =3D +60.0=B0C, hyst =3D +49.0=B0C) sensor = =3D thermal=20 diode CPU Temp: +27.0=B0C (high =3D +60.0=B0C, hyst =3D +0.0=B0C) sensor = =3D thermal=20 diode via_cputemp-isa-0000 Adapter: ISA adapter Core 0: +27.0=B0C I modified my "/etc/sensors.d/local.conf" file to match the outputs=20 shown in "f71805f-isa-0290" to those seen in "via_cputemp-isa-0000" and=20 "acpitz-virtual-0" since there are no corresponding values in my=20 "/etc/sensors3.conf". In this case "temp1" is mapped to "System Temp"=20 and "temp2" is mapped to "CPU Temp" in my "local.conf" file. After studying the code posted on "lm-sensors.org" for the standalone=20 "via_cputemp" module, I think the "via_cputemp" module pulls it's=20 temperature value from a MSR. I did not have the source code handy for=20 my distribution when I did this research, but does one expect=20 differences on what value is being accessed (doubt it)? Perhaps the=20 value being accessed is achieved through a different mechanism? If it=20 matters I will do the research in the FC14 source code. Every time I run "sensors", the value shown in "via_cputemp" is within=20 +-2C or less of the "CPU Temp" value reported by "f71805f". The same=20 (+-2C or less) can be said for the "acpitz" value and the "System Temp"=20 value from "f71805f". Numbers that are that close on a consistent basis=20 are a coincidence that is too good to be true, which is why I suspect=20 Jetway has what could be a simple "label swap error" in their BIOS. If the MSR value read by "via_cputemp" is correct, and I think it is,=20 then I think Jetway has their BIOS labels (what they display on screen)=20 switched for "CPU temp" and "System Temp". I have posted a message to=20 Jetway tech support asking them about this matter. Hopefully they will=20 respond in a timely manner. Does my logic and understanding of the "via_cputemp" code make sense, or=20 have I gotten myself turned around the wrong way on this issue? Thank you. Jeff _______________________________________________ lm-sensors mailing list lm-sensors@lm-sensors.org http://lists.lm-sensors.org/mailman/listinfo/lm-sensors