Stuttering / Frame drops with RS880/785G and AMD Bulldozer CPU

[Shahar Or]

Dear Ones,
Thank you for your replies.

A clue to the mystery has been found and I'm writing about it below.

BTW, Would it count as top posting if I write some of the message here
at the top and some inline or is it OK this way?

First things first: Here's a video(1) of the stuttering / framedrop. I
hope it demonstrated the issue.

Windows 7 runs smooth, without the stuttering / framedrop problem,
with a driver that's been automatically installed from Windows Update
in my LCD's maximum resolution of 1280x1024.

A Live image of Ubuntu Desktop 12.04 amd64 was also tested. It had the
same stuttering / framedrop.

As per Alex's suggestion, attached is glxinfo. It seems to say that
acceleration is on.

Apparently, testing with a dedicated PCI Express GPU (Radeon R300 if I
remember correctly), the stuttering persisted.

2012/2/9 Michel Dänzer <michel at daenzer.net>
>
> On Don, 2012-02-09 at 02:03 +0200, Shahar Or wrote:
> >
> > Since replacing an AMD Sempron 140 with an AMD FX-4100 CPU in my
> > system
>
> Literally only replacing the CPU in the socket, nothing else changed?

Actually, as per Gigabyte's instructions(2), in order to have support
for this CPU, I upgraded the BIOS from the "F2" version to the "F3"
version before replacing the CPU (flashrom FTW!) If it is necessary, I
can put in the old Sempron 140 CPU for testing.

> > I'm experiencing frame drops in practically anything. They seem
> > to be CPU activity related and they are very frequent.
>
> What exactly does 'seem to be CPU activity related' mean? If it means
> the frame drops coincide with high CPU usage, a CPU profile from perf,
> sysprof or oprofile corresponding to a frame drop could be interesting.

First, for clarification, I don't yet know how to use perf, sysrop or
oprofile. So I installed the three of them from the distribution
repositories (reporting a bug along the way(3)) and found out that
perf has a nice long tutorial(4) which I would prefer to abstain from
reading :) if you'll excuse me.

So I ran sysprof, which is an easy GUI and to my content I only needed
to press a "Start" button :). That's when the magic happened. From the
moment it starts the stuttering goes away. Sweet rendering smoothness
of divine electrical display benefaction ensues! And from the moment I
press "Profile" to stop it, it stops and stuttering returns OMG. And
this is perfectly persistent. What does this mean?

> > Please let me know if you think that this could be radeon driver
> > related or something else because I really don't know where to
> > start... I even looked at the AMD cache penalties bug:
> > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/862583
> > But it shouldn't make such a big noticeable problem, right?
>
> That indeed seems unlikely, but you could always try
> applying/disabling/reverting the patch(es) just in case.
>
>
> > The BIOS is latest version.
>
> Does it have proper support for the new CPU?
Like I said, It should have, according to Gigabyte and the absence of
the this problem in Windows 7.

More stuff I tried since replacing the CPU: I have played with BIOS
settings - trying different configurations. I also replaced to a new,
more adequate PSU. I also tried different RAM sticks and different
amounts of them (1, 2 and 4 sticks).

I hope that I can be of furter use in making this board/CPU combo rock in Linux.

Blessings,
Shahar

Links:
1. https://docs.google.com/open?id=0BxH2PmBUnzG4ZjQyMzhkOTgtODJhYi00MDZhLTg2MmQtYjU4Yzg3YzJlNzg3
2. http://www.gigabyte.com/support-downloads/cpu-support-popup.aspx?pid=3817
3. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/931353
4. https://perf.wiki.kernel.org/articles/t/u/t/Tutorial.html
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