Assigning tasks to processors

Using a 16 core machine (2x8), I am performing some parallel processing speed testing. I am using "affinity..." to force certain tasks onto certain processors/cores, and this appears to be working fine. Assuming I set up a 14 task on 14 core run, is there any way I can PREVENT the myriad OS Windows tasks from running on these 14 cores? I want to restrict them to the remaining 2 cores.

Also, while instrumenting certain functions and their calling trees with the real time clock, I notice their duration is always a multiple of about 15.5 milliseconds. Is this a tunable parameter?

Thank you!

CPU affinity is a restriction on processes to use only specific cores. There is no provision for reserving cores for any purpose or imposing restrictions on how individual cores will be used. The system thread scheduler can and will use all cores for any processes, subject to affinity restrictions they may have.

Affinity is a restriction on processes, not on cores.

As a general rule it is best to let Windows manage thread scheduling as it wishes. The goal of this is always to optimize performance. There are complex rules that control this. Manually setting affinity is usually not beneficial. Of course there are a few exceptions.

Most system timing on multi core systems has a granularity of 15.5 ms. This is part of system design and is not user alterable.