Since the design of lock-free data structures often poses a formidable intellectual challenge, researchers are constantly in search of abstractions and primitives that simplify this design. The multiword LL/SC object is such a primitive: many existing algorithms are based on this primitive, including the nonblocking and wait-free universal constructions [1], the closed objects construction [4] and the snapshot algorithms [12, 13].

In this paper, we consider the problem of implementing a W-word LL/SC object shared by N processes. The previous best algorithm, due to Anderson and Moir [1], is time optimal (LL and SC operations run in O(W) time), but has a space complexity of O(N²W). We present an algorithm that uses novel buffer management ideas to cut down the space complexity by a factor of N to O(NW), while still being time optimal.