Hello,
I saw some discussion about problems with video cards introducing latency
into real-time tasks, so I thought I would contribute my experiences in
the matter. I used rtlinux 3pre9 on 2.2.17 kernel, and my usual timing
error (from the examples/measurements test) is about 10usec.
Using XFree86 3.3.6, I tried three different cards,
PCI Trident 3dimage 9750: Scrolling in an xterm caused timing errors to
increase to about 50 usec. Dragging the xterm around the screen or
opening/closing windows caused errors of a few thousand usec.
AGP Cirrus Logic CL-GD5465:
Dragging around and opening/closing windows would cause occasional
timing errors of up to 1000 usec.
AGP SIS 6326:
No problems observed.
Setting the "no_accel" option in XF86Config made any timing problems
disappear.
Frank
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