Temperature monitoring on old desktop - Dell OptiPlex SX270?

Dan Nelson dnelson at allantgroup.com
Sun Aug 3 13:23:11 UTC 2008

In the last episode (Aug 03), Torfinn Ingolfsen said:
> On Sat, 02 Aug 2008 20:19:12 -0700 Jeremy Chadwick wrote:
> > On Sun, Aug 03, 2008 at 01:50:53AM +0200, Torfinn Ingolfsen wrote:
> > The first questions to ask are: 1) does this machine even have a
> > H/W monitoring IC on it, and 2) is it enabled/wired to thermistors
> > and fans?
> Yes, but so far I haven't found out anything by searching.
> > What processor is in it?  Not a Core2Duo.  I'm guessing since it's
> > circa 2004, probably a Pentium 3 or 4, or possibly an older AMD.
> Pentium 4. From dmesg:
> CPU: Intel(R) Pentium(R) 4 CPU 2.60GHz (2593.51-MHz 686-class CPU)
>   Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
>   Features2=0x4400<CNXT-ID,xTPR>
>   Logical CPUs per core: 2
> > None of those, to my knowledge, have on-die temperatures -- they all
> > rely on external H/W monitoring.
> Ok, so what is the 'TM' feature of this cpu then?

>From what I can find on Intel's site for your CPU, TM is an emergency
switch that lowers the CPU speed to pervent overheating that could
damage the processor.  Under normal circumstances, it should never
trip, and its on/off status (not temperature) is only readable by two
pins on the CPU.  It can be disabled and enabled by software, but not


"The Thermal Monitor feature helps control the processor temperature by
activating the Thermal Control Circuit (TCC) when the processor silicon
reaches its maximum operating temperature. The TCC reduces processor
power consumption by modulating (starting and stopping) the internal
processor core clocks. The Thermal Monitor feature must be enabled for
the processor to be operating within specifications. The temperature at
which Thermal Monitor activates the thermal control circuit is not user
configurable and is not software visible."

> > I just checked http://tingox.googlepages.com/sx270 and sure enough, an
> > older P4.  coretemp(4) won't work with this.
> I know, I just thought that ther might be something similar for the
> TM feature of Pentium 4's.
> > I would start by booting the machine into Windows and install
> > SpeedFan.  If that thing is able to detect and provide thermal data,
> Ouch. I was hoping that I wouldn't have to do that. The machine have
> no internal CD-drive, and for some reason doesn't want to boot from a
> (usb) external cd-drive either (kind of funny - it boots from flash
> drives and external hard drives. But cd-rom -no).
> I was hoping to solve this without windows in the picture.

	Dan Nelson
	dnelson at allantgroup.com

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