Re: powernow-k8 and stuck change-pending bit

[John Belmonte <john@neggie.net>]

John Belmonte wrote:
> Devriendt, Paul wrote:
> 
>>>symptoms:
>>>
>>>   After working fine for a while (several minutes to several hours),
>>>cpufreq seems to get into a bad state where:
>>>
>>>    * change pending bit set / stuck kernel messages appear
>>>
>>>    * reloading powernow-k8 module fails, with "change 
>>>pending bit stuck"
>>
> [...]
> 
>>The most likely scenario here is the VRM was unable to change
>>voltage, and that means flaky hardware as it has previously been
>>able to successfully do so. The reason I pick on the VRM and not
>>some sort of issue with the HyperTransport fabric is that it is
>>unlikely anything would still be alive if there was some sort of 
>>problem coming back from the LDT_STOP.
>>
>>Assuming the VRM continues to supply the current voltage within 
>>spec, the system will stay up indefinitely, at the current
>>voltage and frequency.
>>
>>The best path to follow would be to investigate warrantee replacement
>>of the board.
> 
> 
> Thanks for the info Paul.  I've had the motherboard replaced with an
> identical model.  This new board seems to have the same problem, except
> that when a transition finally fails, Linux hangs bad enough to require
> a hard reset of the system.
> 
> With two boards having this problem, it suggests either a bad
> motherboard design or some bad interaction between Linux and the
> motherboard.  (It seems strange that the manufacturer wouldn't have seen
> this problem under Windows.)  Much less likely is that I have a bad CPU.

An update to this story:  I've replaced my motherboard with a different
brand and model (DFI K8M800-MLVF) and am encountering the same power
throttling issue.  It does share the same Via chipset as my previous
motherboard.  I guess the next stop on this arduous trek is to try a
different chipset.

--John