Advanced Synchronization Facility (ASF) is a proposed extension to the x86-64 instruction set architecture that adds hardware transactional memory support.
It contains four new instructions—SPECULATE, COMMIT, ABORT and RELEASE—and turns the otherwise invalid LOCK-prefixed MOVx, PREFETCH and PREFETCHW instructions into valid ones inside transactional code regions.
The SPECULATE and COMMIT instructions mark the start and end of a transactional code region.
Inside transactional code regions, the LOCK-prefixed MOVx reg/xmm, mem, PREFETCH and PREFETCHW instructions can mark up to four cache lines for protected memory access.
Accesses from other processor cores to the protected cache lines result in exceptions, which in turn cause transaction aborts.