There's no limit.
The on-access scanner uses the CPU count in its algorithm for determining how many scanning threads to have available.
OK & Thank you
I think the problem is patch6
Win2012R - VSE8.8 installed with more cores than 64 -- with P6 = BSOD: IRQL_NOT_LESS_OR_EQUAL
Win2012R - VSE8.8 installed with 64 cores or less cores than 64 -- with P6 = works
Win2012R - VSE8.8 installed with more cores than 64 -- with P5 = works
Win2012R - VSE8.8 installed with 64 cores or less cores than 64 -- with P5 = works
You might be hitting upon an issue we recently uncovered due to reports of crashes coming in with Patch 6 installed. And the other telling piece of criteria you mentioned, the CPU count.
We were improperly handling memory addresses on NUMA processors. This could lead to varied types of bugcheck codes, typically crashing on startup (which could appear as a reboot loop).
A fix is expected to be included in our next patch release (patch 7, eta November)