Phenom II 975 BE shows 0 celsius

Andriy Gapon avg at
Mon Aug 1 14:25:57 UTC 2011

on 01/08/2011 03:28 Mario Lobo said the following:
> Hi to all
> In my desktop machine, I had an AM2+ ASROCK mobo with Phenom II 955 BE that 
> showed each core temperature perfectly under FBSD 8-STABLE, via 
> dev.cpu.x.temp. amdtemp.ko loaded.
> Unfortunately this Mobo died and only found AM3 boards for which my phenom 955 
> doesn't fit. So I got an ASUS M4A88T-V EVO with a Phenom II 975 BE. 
> Funny thing. An AM3 phenom II fits on an AM2 board but an AM3 board doesn't 
> accept an AM2/AM2+ phenom II :(.
> Anyway, now, under the very same system, it shows 0 degrees on dev.cpu.x.temp 
> for all cores.

Sorry, I've got lost in all the config changes.  So what system do you have now?
Can please also provide CPU-related information from dmesg?

> I've been looking through k8temp and amdtemp src code. I am definitely not 
> sure of this but I believe something might have happened to those:
> From k8temp.h
> K10_THERM_REG      0xa4 
> K10_CURTMP(val)    (((val) >> 21) & 0xfff)
> K10_THERMTRIP(val) ((val >> 1) & 1)
> From amdtemp.c
> /*
>  * Register control (K8 family)
>  */
> #define	AMDTEMP_REG0F		0xe4
> #define	AMDTEMP_REG_SELCORE	0x04
> /*
>  * Register control (K10 & K11) family
>  */
> #define	AMDTEMP_REG		0xa4
> Output of k8temp -dn:
> CPUID: Vendor: AuthenticAMD, 0x100f43: Model=04 Family=f+1 Stepping=3
> Advanced Power Management=0x1f9
>    Temperature sensor: Yes
>  Frequency ID control: No
>    Voltage ID control: No
>     THERMTRIP support: Yes
>    HW Thermal control: Yes
>    SW Thermal control: Yes
>    100MHz multipliers: Yes
>    HW P-State control: Yes
>         TSC Invariant: Yes
> Temp=c0fef
> ThermTrip=1fc00c30
> 0
> I keep a small win7 partition to test little things like this and see if the 
> same thing happens there, and it doesn't, so I concluded that the sensors are 
> there and are working.
> One thing is worth noting though. I have used a free gadget that shows 
> activity/temp for each core. It worked fine with the previous MB/CPU.That ALSO 
> stopped working with this new MB. Like FBSD, it shows 0 degrees for any core 
> too, although it correctly displays each core load.

Most likely that gadget just re-uses OS-provided information.

> The only windows tool that correctly shows the temperature are the ASUS tools 
> that came with the mobo.
> Other than that, everything is working fine! The only thing I had to fix was 
> the fstab ada location.
> I know this is not a big thing but I got accustomed to keeping an eye on those 
> temperatures.
> I have googled for a few days now searching for Thermal register address or 
> offsets for the Phenom II 975 BE, or anything related to this problem and 
> found nothing. Every search on AMD site was fruitless. I could not find a 
> single bit of tech info on this processor there, or any other tech info for 
> that matter.
> Would any one have any pointers/clues/suggestions on this?

I would try to add some printfs (or used dtrace - whichever is easier for you) to
see what's going on.  Or you can even use pciconf to directly sneak a peek at
what's reported by the hardware, e.g.:
# pciconf -r pci0:0:24:3 0xa4

You can read the BKDG to see how to interpret the value - search for F3xA4.  See
F3xE4 for offset calculation.

Hopefully you should be able to see if hardware reports sane value and how the
amdtemp ends up reporting 0°C.

Andriy Gapon

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