New x86 processors enhanced the operation of the REP MOVSB and REP STOSB instructions. A processors supports these enhancements if CPUID.(EAX=07H, ECX=0H):EBX[bit 9] is 1 (ERMS bit). VM uses stosq/stosd instructions to zero new java objects, replace them with fast-string stosb instructions when they are available. Note: we can't use REP MOVSB for arraycopy because it is not JMM compliant (not atomic and out of order).