Coretemp seems to be off quite a bit

[Frank Shute]

On Tue, Oct 07, 2008 at 06:28:32AM -0700, Jeremy Chadwick wrote:
>
> On Tue, Oct 07, 2008 at 02:25:17PM +0100, Frank Shute wrote:
> > On Mon, Oct 06, 2008 at 09:39:40AM -0500, Kirk Strauser wrote:
> > >
> > > I have a Gigabyte motherboard with an Intel ICH-9 chipset, and a  
> > > 3.0GHz Core 2 Duo (E8400).  The coretemp sysctls seem to always show  
> > > 50C as the baseline temperature:
> > > 
> > > $ sysctl dev.cpu | grep temp
> > > dev.cpu.0.temperature: 50
> > > dev.cpu.1.temperature: 50
> > > 
> > > This is with a big PSU fan, a good CPU fan, a clean heatsink, and two  
> > > case fans aimed the right direction (front fan pulling cool air in,  
> > > rear fan pushing warm air out).  If I reboot and go into the BIOS, I  
> > > get numbers around 42-43C.  I know it's kind of hard to compare  
> > > directly, but the coretemp numbers are from a totally idle system with  
> > > powerd scaling it back to 373MHz, so it should be as cool as when  
> > > sitting idle in the BIOS screens.  When I work the system hard, like  
> > > running "make -j4 buildworld", I see temperatures up around 63-64C,  
> > > and I'm almost positive that's not right.
> > > 
> > > Any ideas why coretemp and the BIOS would show such different numbers?
> > 
> > To add some numbers, I've got an E6550 on a Gigabyte GA-P35-DS3L
> > (ICH9) and I get:
> > 
> > $ sysctl dev.cpu | grep temp
> > dev.cpu.0.temperature: 24
> > dev.cpu.1.temperature: 28
> > 
> > Ambient room temp: 23°C
> > 
> > That's running powerd and the machine idle, standard heatsink/fan
> > combo, 1x12cm case fan.
> > 
> > Your's might run hotter (higher clock speed? Mine: 2.33GHz) but I
> > wouldn't expect it to run *so* much hotter.
> > 
> > I'd expect your numbers to be right if all the ACPI stuff is working.
> 
> Clarification here is needed:
> 
> coretemp(4) has nothing to do with ACPI.  It gets thermal statistics
> from the processor by talking *directly* to the processor with specific
> opcodes, the results returned in specific CPU registers.  It does not
> rely on ACPI.

Thanks for the clarification.

What I meant was that the core temperatures are dependent on clock
speed which is dependent on powerd which is dependent on ACPI, if I'm
not mistaken.

i.e: If powerd isn't working properly due to ACPI bugs then you may
have your CPU running at full clock, hence high temps. No?

So one possible scenario is that powerd isn't working, although Kirk
implies that it is.

One piece of evidence that powerd is not working properly is that it
clocked the CPU back to 373MHz - which seems an odd-looking number to
me.

On my machine:

$ sysctl dev.cpu | grep freq
dev.cpu.0.freq: 250
dev.cpu.0.freq_levels: 2333/22464 2041/19656 2000/22464 1750/19656 1500/16848 1250/14040 1000/11232 750/8424 500/5616 250/2808

i.e: I've got 2 odd steps high up but the rest are divisible by 50.

I don't know if Kirk has fiddled with powerd. I just installed it &
started it.

Even if he used a percentage, it still seems a weird number - unless I
missed something in powerd(4).

Regards,

-- 

 Frank 


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