Performance of simultaneous multithreaded multimedia-enhanced processors for MPEG-2 video decompression

This paper explores microarchitecture models for a simultaneous multithread ed (SMT) processor with multimedia enhancements. We start with a wide-issue superscalar processor, enhance it by the SMT technique, by multimedia unit s, and by an additional on-chip RAM storage. Our workload is a multithreade d MPEG-2 video decompression algorithm that extensively uses multimedia uni ts. The simulations show that a single-threaded, 8-issue maximum processor (assuming an abundance of resources) reaches an instructions per cycle (IPC ) count of only 1.60, while an 8-threaded 8-issue processor is able to reac h an IPC of 6.07. A more realistic processor model reaches an IPC of 1.27 i n the single-threaded 8-issue vs 3.03 in the 4-threaded 4-issue and 3.21 in the 8-threaded 8-issue modes. Our conclusion on next generation's micropro cessors is that a 2- or 4-threaded 4-issue processor with a small on-chip R AM accessed by a local load/store unit will be superior to a wide-issue (si ngle-threaded) superscalar processor at least for MPEG-2 style video decomp ression algorithms. (C) 2000 Elsevier Science B.V. All rights reserved.