FC5 2.6.17 runs hot with Athlon / athcool

[Martin Ewing]

Martin Ewing wrote:
> Klaasjan Brand wrote:
>> On 7/10/06, *Martin Ewing* <ewing at ewing.homedns.org 
>> <mailto:ewing at ewing.homedns.org>> wrote:
>>
>>     I am running 2.6.17-1.2145_FC5 on an Athlon XP2000+ using 
>> athcool.  On
>>     previous kernels, my CPU temperature was about 39 C with athcool 
>> on or
>>     50 C with athcool off.  That was really nice, allowing me to run a
>>     slow
>>     fan, etc.  I had no stability problems.
>>
>>     With the present kernel and athcool on, I get 46 C, rising to ~50
>>     C with
>>     athcool off.
>>
>>
>> Maybe there's some process hogging the CPU so it runs hotter? Did you 
>> try with athcool off?
>>
>> Klaasjan
> Exact same setup, zero apparent load factor.  (As I said, Athcool off 
> --> ~50 C with any kernel.)
>
> I had a similar problem with older kernels after using a USB drive and 
> then unmounting and disconnecting it.  Apparently (WAG), the USB 
> driver keeps scanning the ports fast enough to prevent the Athlon from 
> sleeping.  Maybe the 2.6.17 kernel does this all the time.
>
> Martin
>
I have narrowed down the problem to the USB area, and submitted as 
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=198264 .  It turned 
out to be a lot easier to characterize the problem by monitoring actual 
120 VAC power of my system using a "Kilawatt" device instead of CPU 
temperature.  Quick results for my system:

Athcool off: 167 W
Athcool on: 122 W (when operating normally)
USB device(s) plugged in: 142 W (no I/O or visible CPU activity)

Once power jumps to 142 W, you need to reboot to get back to 122 W.

The Athlon CPU power saving feature can give you a significantly cooler 
running system.  Shame that the USB driver seems to break it, at least 
partly.

Martin