Performance of a micro-threaded pipeline
Bing Luo, CHRIS R. JESSHOPE · 2002
The micro-threaded microprocessor is a chip multi-processor, which uses a multi-threaded approach, where the threads are obtained from within a single context and exploit both vector and instruction level parallelism (ILP). This approach employs vertical and horizontal transfer in a simple pipeline. The horizontal transfer is referred to as the normal scalar pipeline processing used in most microprocessors. Vertical transfer is a context switch, which allows the code to tolerate any latency from undetermined data and control dependencies. The performance of the single pipeline is very important in the overall performance of the whole processor, which can distribute threads to any of the available processors. We have measured the influence of three crucial parameters - cache delay, cache miss rate, and number of registers - on the performance using our simulator. Even for a long cache delay (1000 processor cycles) we found that the micro-threaded pipeline can still achieves an IPC of 0.8 in the peak performance which is some 6 times better than a conventional scalar pipeline. If we further degrade cache performance by using an artificially small cache line size the performance of conventional scalar pipeline gives an IPC of 0.02, whereas with unlimited registers the micro-threaded pipeline still manages to achieve and IPC of 0.8 (a factor of 40 difference in performance). processing used in most microprocessors. Vertical transfl is a context switch, which allows the code to tolerate any latencyfte undetermined data and control dependencies. Theperf0E2C.k of the single pipeline is very important in the overallperflC0804 of the whole processor, which can distribute threads to anyof the available processors. We have measured theinf0Eqk8 of three crucial parameters - cache delay, cache miss rate, and numberof registers - on the perfAA2C.k using our simulator. Evenfe a long cache delay (1000 processor cycles) wefC08 that the micro-threaded pipeline can still achieves an IPCof 0.8 in the peak perfq04C.8 which is some 6 times better than a conventional scalar pipeline.If wefCEq4W degrade cache perfC0qW4q by using anartif8C.84W small cache line size the perfqW48C. of conventional scalar pipeline gives an IPCof 0.02, whereas with unlimited registers the micro-threaded pipeline still manages to achieve and IPC of 0.8 (afCEq0 of 40difW0WC.8 in perfWk2C.80q Keywords: micro-threaded pipeline, scalar pipeline, micro thread, perfd,C0qEA0C.8W8E8Cf 1.