you could try the below exthreads should be 0 for auto detect or 7 for quadcore - below from
https://community.bistudio.com/wiki/Arma2:_Startup_Parameters
-exThreads=<number> Change to a number 0,1,3,5,7. This will override auto detection (which use 3 for dualcore and 7 for quadcore).
also...