I am guessing that the problem is Karmic (Ubuntu 9.1) because Dotsch_UX (8.1) runs collatz at nice=10 just fine. Unfortunately, in 9.1, collatz is running at nice=19 and cannot get enough of the cpu to feed the GTS250 as I just discovered.

Rather than repost everything, here is a link to the problem.

There is also an interesting discussion here where it is pointed out that the GPU time is substituted for the CPU time when reporting time back to boinc. It would appear that is one way to avoid the low cpu time problem.

If boinc "dispatches" a task, such as collatz, could it not set nice to a smaller number such as 10 or even 0 if it knew that the cpu load was very low?

Ok - I finally got collatz to run at nice=0 in Karmic which solved my GPU feeding problem. I also learned something (possibly)

I installed the recent (2.3 actually) linux cuda toolkit from nvidia. After doing ldconfig, the tool ldd ...collatz... showed that I was now using the 2.3 version and that seems to have got me nice=0. So - I am assuming the problem was using an older library, 2.2, that came with the collatz linux package. That one was showing nice=19.