Clustering is an architectural technique that allows the design of wide superscalar processors without sacrificing cycle time, but at the cost of longer communication latencies. Simultaneous multithreading architectures effectively tolerate instruction latency, but put even more pressure on timing-critical processor resources. This paper shows that the synergistic combination of the two techniques minimizes the IPC impact of the clustered architecture, and even permits more aggressive clustering of the processor than is possible with a single-threaded processor.

Additionally, this paper shows that multithreading enables effective instruction steering policies unavailable to a single-threaded clustered architecture. This paper explores the impact of aggressively clustering four complex processor structures, (1) instruction window wakeup and functional unit bypass logic, (2) register renaming logic, (3) the fetch unit, and (4) the integer register file, on a simultaneous multithreading processor.