AFAIU, LL/SC is the more generic, powerful primitive. In theory LL/SC can be used as the hardware primitive for a much broader range of lock-free algorithms, as

AFAIU, LL/SC is the more generic, powerful primitive. In theory LL/SC can be used as the hardware primitive for a much broader range of lock-free algorithms, as well as for software transactional memory generally. CAS algorithms are more commonly seen because it's the lowest common denominator, and the best x86 offered. But because of the limited number of addresses that can be monitored in hardware without sacrificing performance or efficiency, in practice LL/SC implementations are weak and only slightly more useful than [double] CAS.