recent testing...

[N Nolan]

So, I came across an issue that few people are adressing due to its
spacific nature.
Its to do with the new-ish kernels KMS system and older intel graphics
cards. My test is on a gm945, and I have read about this issue with
other ones up to the gma965.

The newer ideas with the KMS system is that it takes the graphics
driver implimentation and brings it lower on the abstraction layer so
that X.org no longer has full control over the graphics driver. It's a
lot smoother this way and the drivers seem to be more stable like
this, but the transition over the past year or two has been quirky.

https://wiki.ubuntu.com/X/KernelModeSetting I think this one's old,
but its more accurate than my description for better reference.

Try just for an idea of what I mean by running the command glxgears.
On a lot of machines the outputs will be in the hundreds of frames per
seconds, while on a lot of the newer glx will limit the fps to 60fps
or whatever your screen refresh is in hz. This is a good thing, the
newer glx' vsync option was written so that it displays the fps
exactly when the screen refreshes, rather than redrawing the program
image two or three times before the screen even refreshes. that wasted
cpu cycles.

The real issue with some of the Intel cards is currently that
something can't handle the vsync correctly. if you're maxing out at 40
and averaging at about 25-30fps, this means that its missing the
alignment with the monitors refresh rate by about half. The command
glxgearss is not really a good program for benchmarking your system,
but it is a good program to test the sync and other basic rendering
with.

try:
sudo export vblank_mode=0 &
and then run glx gears again, or test it with another graphics program
like pj64 under wine. You could also see a difference in armagetronad,
another one of my favorite games

This work around disables the vsync so that it will waste those cpu
cycles redrawing the screen, like it used to do. But, it's a definite
improvement for those getting half of their screen's refresh rate on
their graphical programs. The problem with this temporary work around,
is that it doesn't stick. the command only holds true for the
xsession. I would recommend from here, adding the line to a init
script. perhaps somewhere in /etc/rc5.d . you can also add it at the
startup of the graphical environment, if you have sudoers set to not
require a password (unsafe).

[Sara Streeter]

That's fascinating - have you posted this on any Linux forums?  If not, you totally should.

Sara

--
Sara Streeter
401.484.7272