Compaq W8000 Hyper-Threading Technology, New Feature of Intel Xeon Processor - Page 19

Hyper-Threading Technology, New Feature of Intel Xeon Processor White Paper 19 Analysis The Montecarlo application is multi-tasked as well as computationally intensive. A task could utilize all of the processor resources, which is determined by the fact that the ratio between the physical 1P (30.1) and physical 2P (15.15) is almost 2:1. Independent of the 1P or 2P case, Hyper-Threading technology does not yield any performance gain since the benchmark is resource bound. See Figure 15. Lower is better Montecarlo Benchmark on Windows XP 35.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00 Enable Disable 30.10 30.27 1P 30.10 30.27 15.15 15.00 2P 15.15 15.00 Figure 15: Verilog Compiled Simulation Benchmark The Verilog Compiled Simulation (VCS) benchmark script includes four independent tasks that run at the same time. Each task simulates the same reset sequence of a memory controller. The VCS benchmark is very memory intensive. Analysis This VCS application is multi-tasked as well as memory intensive. A task requires about 20MB of data for simulation. The data cache is shared between the two threads, which results in frequent cache line replacement and hence shows poor performance when Hyper-Threading is enabled. In a two physical processor case with Hyper threading disabled, with cache available on each processor, there is a significant improvement in performance. With Hyper-Threading technology enabled in a dual processor configuration, the performance is worse than just a true dual processor configuration. This poor result is due to the sharing of resources between the same processor and checking the other processor's cache validity for correct data. See Figure 16. 167T-0202A-WWEN