[ILUG] nvidia & sound interrupt problems

[John P. Looney]

 I think someone was asking on the list about problems with 2.6, Nvidia
and sound interrupt problems. I found this:

  http://home.t-online.de/home/Bernhard_Kuhn/rtirq/20040304/rtirq.html

16. High Latencies with NVIDIA video cards

When starting or exiting 3D applications, you may recognize latencies up
to 100 microseconds. This missbehaviour has been identified as a "wbinv"
instruction in the function os_flush_cpu_cache() in file nv.c of the
NVidia kernel driver. This instruction invalidates/flushes the CPU caches,
what is certainly a bad idea. So if you intend to use 3D graphics in your
hard real time system, you should start the 3D application before you
start the real time process (shutdown the other way round). There have
also been some rare latencies between 10 and 40 microseconds observered
while a 3D application is running. The instructions causing this effect
have been identified as in/out instructions and nvidia hardware register
accesses. Maybe there are some AGP abitration issues. This subject is
still under investigation. With a 2 GHz Athlon CPU, you can savely
operating the APIC timer at 10 KHz whitout loosing interrupts.

John