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

[Jean-Yves Avenard]

Hi

On 24 October 2010 05:48, faginbagin <mythtv at hbuus.com> 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 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.

When AMD Coon n'Quiet is enabled, the default governor set the bus
speed too low to properly feed the nvidia card for VDPAU usage. As
such, VDPAU is unusable. Set the minimum frequency to be around
1.8GHz.