The processor affinity of a thread is the set of processors it has a relationship to. In other words, those it can be scheduled to run on.

ProcessThread.ProcessorAffinity represents each processor as a bit. Bit 0 represents processor one, bit 1 represents processor two, and so on. The following table shows a subset of the possible ProcessThread.ProcessorAffinity for a four-processor system.

You can also specify the single, preferred processor for a thread by setting the ProcessThread.IdealProcessor property. A process thread can migrate from processor to processor, with each migration reloading the processor cache. Specifying a processor for a thread can improve performance under heavy system loads by reducing the number of times the processor cache is reloaded.