[mythtv-users] CPU performance governor vs disabling AMD Cool n Quiet

faginbagin mythtv at hbuus.com
Sat Oct 23 18:48:34 UTC 2010


First some background to my questions, and to hopefully help anyone who 
encounters the same problem:

I "upgraded" my sister's mythtv box, replacing an older ECS mobo/AMD 
Sempron 32 bit single core CPU with an ASUS M3N78 PRO mobo/AMD Athlon X2 
4850e dual core cpu. The "new" computer used to be my mbe/fe and had 
worked fine with two HVR-1600 cards. But with her PVR-150 and a HD-5500, 
she's been having trouble with the PVR-150 choking after a few days of 
recording. I think the problem was due to me enabling AMD Cool n Quiet 
in the BIOS (it was disabled by default). She's been sensitive to fan 
noise, so although it wasn't enabled when the computer was mine, I 
thought I would enable it for her.

The problem manifested itself with an incomplete recording after 2-7 
days of uptime, followed by completely failed recording attempts plus 
dmesg output filled with messages like:
ivtv0: DMA TIMEOUT 00000001 0

Turning on debug output in the ivtv driver showed these two messages of 
interest at the time recording began to fail:
ivtv0:  warn: DMA ERROR 00000003 00000000 00000013 0
ivtv0:  warn: DMA ERROR 00000003 00000000 00000011 2

The only way to get the PVR-150 to work was to reboot. Stopping the 
mythbackend, unloading/reloading ivtv and restarting mythbackend didn't 
clear the problem.

I think I have solved the problem by changing the CPU frequency governor 
from ondemand to performance. It's only bee a week, so I'm going to give 
it another week, and if I get no more failed recordings, I will declare 
success and make the change permanent. My questions are:

Should I change the BIOS setting to disable AMD Cool n Quiet or do 
something to make the CPU frequency governor = performance at boot time?

Is there a difference, any advantage using one method over the other, 
any gotchas?

Also, has anyone seen a difference in the performance of the M3N78's IGP 
(nVidia 8300) with these various tweaks?

I ask because the performance of the IGP has been disappointment with 
Cool n Quiet enabled and the ondemand governor. I never used the IGP 
since I've still got an SD TV. The IGP is barely able to play 1080i 
content with the VDPAU slim profile. Such content is unwatchable with 
VDPAU normal. I'll get a chance to see if it's any better with the 
performance governor tomorrow. If not, it looks like I'll have to get 
her a GT 220 GPU.

TIA,
Helen


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