David B. Papworth

Architecture and implementation of a VLIW supercomputer

Very-long-instruction-word (VLIW) computers achieve high performance by exploiting the fine-grain parallelism present in sequential or vectorizable code. Multiflows /200 and /300 VLIW systems yielded near-supercomputer performance by this means despite the relatively slow (65 ns) clocks. With its much faster clock period (15 ns) and architectural improvements, the new /500 system attains approximately 4-9* the performance of its predecessors. The authors describe the /500 architecture and implementation (i.e. TRACE/500), with special attention paid to the tradeoffs involved in designing very-high-speed VLIWs.<<ETX>>

A VLIW architecture for a trace scheduling compiler

Very Long Instruction Word (VLIW) architectures were promised to deliver far more than the factor of two or three that current architectures achieve from overlapped execution. Using a new type of compiler which compacts ordinary sequential code into long instruction words, a VLIW machine was expected to provide from ten to thirty times the performance of a more conventional machine built of the same implementation technology.Multiflow Computer, Inc., has now built a VLIW called the TRACETM along with its companion Trace SchedulingTM compacting compiler. This new machine has fulfilled the performance promises that were made. Using many fast functional units in parallel, this machine extends some of the basic Reduced-Instruction-Set precepts: the architecture is load/store, the microarchitecture is exposed to the compiler, there is no microcode, and there is almost no hardware devoted to synchronization, arbitration, or interlocking of any kind (the compiler has sole responsibility for runtime resource usage).This paper discusses the design of this machine and presents some initial performance results.