Public bug reported:
---Fresh install of Ubuntu 8.04
Found the ati drivers 2d and 3d accel to work fine, with the exception of
flash. Flash performance is slow, choppy and reveals horrible motion blur
watching a 480p movie on hulu. No horizontal lines on the desktop whatsover,
this what I refer to as "flicker". Its hard to describe but it appears to be
simply the vertical refresh of pixels skips lines... underscan/overscan? I
dont know.
---Fresh install of Ubuntu 8.10
Immediately after installing the proprietary drivers and rebooting, the desktop
became almost useless as hundreds of random horizontal lines covered the left
half of the screen. Thinking this was a bad install I cksum'd the iso, then
reinstalled fresh and reattached the driver. Same result.. At this time I
thought it was simply the typical lousy ATI drivers and reverted back to 8.04
to live with sub-par flash performance but a usable desktop.
---Fresh install of Ubuntu 9.04
I can't resist new toys...
Exact same issue though. I searched google for hours looking for another
complaint on these lines, found similar issues but none of the workarounds
resolved. Being determined to play with this load and after many reinstalls
I noticed a pattern to these horizontal lines. The lines reduced and almost
disappeared when I ran fgl_glxgears?
Odd I thought but sure enough readily reproduceable. Another oddity
... after running fgl_glxgears for 30 seconds or so I saw my frame rate
drop from 400fps to ~200fps. Subsequent startup of fgl_glxgears kept my
framerate to 200fps until rebooting.
With this I found message logs stating "clocksource tsc unstable", yet
no message that it chose another clocksource... With that I decided to
add "notsc" to my kernel line... didn't stop the lines... did stop the
unstable warnings.
Thinking some sort of timing issue and "load -- fgl_glxgears" apparently
reduced the lines I decided to run
"nice dd if=/dev/zero of=/dev/null" to artificially load the cores on the cpu.
HOLY clear screen batman.. The lines were gone and when I say gone I mean not
even a single pixel out of place.
Now I am on to something here.. I had followed the ATI wiki suggestions
to "turn off effects", "tweak overlays" and all sorts of things to drop
this flicker... none really reduced them. Putting this artifical load
on the cpu's cleared up the artifacts completely.
More tests I ran...
Back to this fps oddity observed in fgl_glxgears...
With notsc set , and "nice dd if=/dev/zero of=/dev/null" running...
fgl_glxgears remains at 400fps consistently and no flicker is observed
anywhere.. desktop or 3d window.
With notsc not set (apparently hpet timing), and "nice dd if=/dev/zero
of=/dev/null" running...
fgl_glxgears starts out at 400fps, drops to 200fps and remains there
until reboot, no flicker.
CPU ondemand.
When my cpu slows are speeds up... the # of random horizontal lines
increases.
Disabling ondemand using the scaling widget and manually setting the CPU to
2.50ghz (max rated) seems to
keep most lines away.
So I am not sure if this is a ATI driver problem or a kernel timing problem?
Hope this helps someone. For now I will simply nicely load the cpu's when I
want a clear desktop or movie :)
-don
ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
MachineType: System manufacturer System Product Name
NonfreeKernelModules: fglrx
Package: linux-image-2.6.28-11-generic 2.6.28-11.40
ProcCmdLine: root=UUID=9078557b-c77b-4e32-9884-fab3ac332bcc ro quiet splash
notsc
ProcEnviron:
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.28-11.40-generic
SourcePackage: linux
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug
--
ati driver 2.6 kernel timings 2d desktop random horizontial flicker
https://bugs.launchpad.net/bugs/355262
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