Conflict-free accesses to strided vectors on a banked cache

With the advance of integration technology, it has become feasible to implement a microprocessor, a vector unit, and a multimegabyte bank-interleaved L2 cache on a single die. Parallel access to strided vectors on the L2 cache is a major performance issue on such vector microprocessors. A major difficulty for such a parallel access is that one would like to interleave the cache on a block size basis in order to benefit from spatial locality and to maintain a low tag volume, while strided vector accesses naturally work on a word granularity. In this paper, we address this issue. Considering a parallel vector unit with 2ⁿ independent lanes, a 2ⁿ bank interleaved cache, and a cache line size of 2^k words, we show that any slice of 2^n+k consecutive elements of any strided vector with stride 2^rR with R odd and r ≤ k can be accessed in the L2 cache and routed back to the lanes in 2^k subslices of 2ⁿ elements.