Is there a way to limit CPU usage to 1 processor on a multi-processor machine. I have a 4 core machine and MilkyWay@Home N-Body Simulation uses all four cores thereby limiting WU processing.

There is a way, but I didn't understand what the problem is. If you were to limit CPU usage to 1 core (25% relative or 1 absolute in your preferences), surely that would limit WU processing?

If, however, you want to prevent N-Body WUs from hindering GPU work, that's already taken care of: The small portion of CPU work that the GPU WUs need takes priority over CPU WUs.

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HI,
Doesn't it make sense to run other WU's utilizing the other 3 cores instead of monopolizing all 4 on 1 WU?

Ah, I see.

Performance-wise, I think one multi-threaded task can be just as efficient as several single-threaded ones. In other words, it can run four times as fast on four cores than it would on one.

However, I've seen at least one example where multi-threaded means incompatible: The GPU_ATI_5k science app over at DNETC. That one tries to use all available graphics processors, and although some have claimed success on two cards after a clean install of some driver versions, I've never gotten anything but errors on my four. My point is, when BOINC is so totally geared towards distributing tasks among several processors (be that GPUs or CPU cores), why do they bother? (Like... If you have four kids successfully riding to school each on their own bicycle, why would you even try to weld all those bicycles together?)

Oh well, back on track, I don't think you'll se any performance hit from having all four cores serve one N-Body WU.

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HI,
Doesn't it make sense to run other WU's utilizing the other 3 cores instead of monopolizing all 4 on 1 WU?

No

I wish my GPU could be of service, unfortunately (or not) I use Macs and Bionic has not found the resources to write programs for us Mac heads. CPU's vs GPU's ? GPU's win hands down. Such is life.