- Try to use REP MOVSB when the size of the transfer is above a certain threshold
- This threshold is determined by the ERMS and FSRM cpuid flags
- The threshold values are (roughly) taken from GLIBC
- A threshold of 0xFFFFFFFF indicates that the cpu has neither flag
- Also detect the new RTM_ALWAYS_ABORT bit in cpuid
- This new bit indicates that RTM is disabled in the microcode
- On cpus with RTM_ALWAYS_ABORT TSX can be renabled by writing 0x4 to the msr 0x0000010F