If you set affinity mask to another value e.g. 84 (that is, you set a bit representing a processor to 2-4-6), those processors are selected for thread assignment.
When you set affinity mask to 0 (the default), the 64-bit versions of Windows, scheduling algorithms set the thread’s affinity.
When you set affinity mask to any nonzero value, affinity interprets the value as a bit mask that specifies those processors eligible for selection.
What happens when you set AffinityMask=84
Translated from decimal 84 to BINAIR this is 0 1 0 1 0 1 0 0
The number of the processor is
7 6 5 4 3 2 1 0
Read from the right to the left
CPU7 CPU6 CPU5 CPU4 CPU3 CPU2 CPU1 CPU0
If you want to activate an ‘unused’ processor, you could use affinity mask value.
The standard FSc value of AffinityMask=-1 meaning that all processors are activated for thread assignment.
Which in conclusion give us the advise not to change the standard affinity mask value.