Intel Transactional Synchronization Extension.<p>When it works, you get support for database-like transactions on RAM (only small transactions, it isn&#x27;t black magic).<p>When it fails, you get all kinds of random crashes at random times.<p>Introduced in Haswell, turned out to be buggy and Intel famously disabled it with ucode update. Since then, they quietly disabled it also for several Broadwells and Skylakes which didn&#x27;t fare much better than Haswell.<p><i>edit: it seems I misread parent&#x27;s post as &quot;what is TSX&quot;</i>