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

[faginbagin]

Michael PARKER wrote:
>>
>> 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 disappointing 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.
> 
> Helen,
> 
> How much main memory are you allocating to the IGP? 
> 
> I'm running a M3N78-EM mobo and noticed that a recent BIOS update permitted up to 512MB to be allocated (vs. the 256MB permitted by the as-shipped BIOS). My M3N78-EM is running with 4GB of DDR2-1066, an AthlonII X4 605e, and Cool n'Quiet enabled. 
> 
> 1080p playback with VDPAU appears to work without problems - the only graphical issues I'm aware of relate to the x64 Beta Flash plug-in apparently being unable to display some Flash content fullscreen (horizontal flashing/breakup).
> 
> Mike

Hi Mike,

Yes, I have updated the BIOS and I've got 512MB dedicated to the IGP.
Perhaps the reason why it's working well for you is because you've got
an Athlon II, which, as Kevin mentioned, doesn't reduce bus speed with
CPU speed.

An update: I took my kill-a-watt over to my sister's and found the power
draw at idle was pretty much the same no matter what the CPU frequency
was set to, within 2 watts. And it seemed to me that playback of 1080i
content was smoothest at the max CPU frequency. So I took the easy route
and just disabled Cool n Quiet in the BIOS. That way, I've got fewer
things to remember to configure when the time comes to install a newer
OS/distro.

FWIW, at max CPU frequency, VDPAU Normal with closed captions wasn't
smooth. So, back to VDPAU slim. She's happy with the playback quality,
so I probably won't get her a video card in the foreseeable future.

Again, many thanks for everyone's help,
Helen