On Thursday, September 12, 2002, at 08:57 PM, Niall Dalton wrote: On Wed, 11 Sep 2002, Bernie Zenis wrote: As far as I am aware, there has been no work done on the possibility of removing speculative instruction execution, out of order instruction execution, nor branch prediction in SMT processors. Some/All of those There has been some work comparing an in-order and out-of-order SMT processors: S. Hily, A. Seznec `` Out-Of-Order Execution May Not Be Cost-Effective on Processors Featuring Simultaneous Multithreading '', IRISA Report No 1179, March 1998, short version appears in proceedings of HPCA-5, Orlando, Jan. 1999. The report is available from http://www.irisa.fr/caps/PROJECTS/Architecture/CacheArchitecture_US.html# SECTION04 It comes down to the fact that if you are going for maximum throughput and ready threads are available, then an in-order SMT gives almost the same performance as an out-of-order SMT. Last I heard, the SMT simulator is still Alpha only. Anyone been working on a PowerPC version? SMTSIM is still Alpha only afaik. One other simulator worth checking out is James Burns' (ex-USC, now with Intel) simulator that allows one to explore the tradeoffs between SMT, chip-multiprocessor (CMP) and a mixed SMT/CMP. It is based on SimpleScalar, which now also has a PowerPC frontend. It may be possible, with sufficiently motivated hacking, to come up with some version combining those.. I would assume that IBM's internal simulator - which _may_ be available for academic usage - can simulate SMT PowerPC as this is due for Power 5 I believe. Thanks for the info. I'm not someone who is "in-the-loop." So I usually just check http://www.cs.washington.edu/research/smt/ occasionally for new papers or new links to satisfy my curiosity for "What's new in SMT." However, it seems to me that that site isn't the central location for all things SMT as strongly as it used to be. SMT is just getting too popular; darn! :-). If you have any other good places to look for SMT activity, I'd appreciate knowing them. -Bernie _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.