Is it normal for the CUDA applications to slow your computer right down?  I find that when I am running CUDA work units, my computer becomes very slow and unresponsive.   I can run optimized units on all four cores without any problems, but shortly after a CUDA unit starts, my system hangs.  It is fine once I put BOINC to sleep for a bit so I can finish what I was doing.

I am thinking it could either be a power issue or more than likely a heat issue.  Anyone else have this happen to them?

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Short answer:
This is a classic problem with CUDA. It has issues crunching extreme angles, especially VLAR units.
Assuming you have installed one of the Lunatics optimized clients, give this perl script a try:
http://lunatics.kwsn.net/12-gpu-crunching/cpu-gpu-rebranding-perl-script.0.html
It allows you to assign VLAR and VHAR wu's to the cpu, and medium angle wu's to the GPU. In theory that should circumvent the problem altogether.
I haven't used the script myself yet, so you'll have to post questions in that forum.

Long answer:
Crunching with CUDA is a work in progress. In general, the problems have diminished with the release of newer optimized apps, improved nvidia drivers, and better CUDA libraries. The severity of the problem varies from user to user. The early 8600/8800 series of video cards seem to suffer the most, possibly because they don't support all of the CUDA math functions.

I have an 8800GTS 640 that I bought cheaply from a friend. It was a nightmare trying to run CUDA in the early days. Not only slowdowns like you've seen, but also nvidia driver crashes and VLAR wu's that aborted with errors.

In May I did find a configuration that ran well, and I intended to share it with you. However, while I was preparing my answer, I discovered that my setup is considered obsolete. In fact, the client I'm running has been withdrawn, replaced by the final beta apps at Lunatics. I'm mulling over whether I should update or simply stick with what works. No doubt the newer client has important optimizations. On the other hand, I'd rather die than go through another round of problems.

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"All really intelligent people should be cremated for reasons of public safety" -- The Amazing Screw-On Head

Certainly is. Boinc Manager/Advanced/Preferences/Computing Allowed: uncheck Use GPU while computer is in use

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Co-owner, the Group of 10 100 200 300

Made your link clickable Mike.

Read about that app on the Berkeley boards. People seem to like it.

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