On Tuesday, September 10, 2002, at 01:41 PM, Jim Magee wrote: On Tuesday, September 10, 2002, at 01:16 PM, Bernie Zenis wrote: Is anyone here familiar with Simultaneous Multithreading (http://www.cs.washington.edu/research/smt/)? Does anyone know if Darwin would lend itself well to SMT? For example, if a SMT PowerPC chip came out, would it be easy to port Darwin to it? I realize that might depend on what kind of SMT architecture was implemented. I have always felt that Darwin works best on an SMP machine. There are enough system threads, and multi-threaded applications to want two CPUs in many "peak" CPU utilization situations (my Mac OS X system typically has ~200 threads). I think the real world anecdotal evidence bears this out as well (most people with dual-ies are quite happy with the responsiveness of their machines, even when compared to single processor machines of quite higher clock rates). All of this is one of the reasons Apple ships all their PowerMacs as dual processor machines right now. The CPI numbers under most of those situations indicate that an SMT (others call it Hyper-threading) processor might do reasonably well compared to an SMP machine. But as you say, it all depends on the particular SMT design and other architectural factors on any given processor. I've always know that modern computers are doing many things at once; but, I didn't really realize (because I lived in Mac OS 8/9 land :-) how many things that was until I got X installed and looked at outputs of programs like top. Obviously, most of those threads are not demanding a lot of the machine during much of the time (otherwise my CPU Monitor load would be much higher). I had thought many years ago that computers would benefit from a processor design like SMT, I just didn't know that it had a name and that people we're working on it until a few years ago. (You would think that a college professor teaching an MP class would know.) I see that real SMT processors are finally being built which makes me happy. I just didn't know if Darwin had its foot in any of it. I'm thinking that for an SMT processor to become a real possibility for replacing (S)MP designs that the "thread" in SMT would have to refer to a full fledged process (eg, own address space, etc.). Would it be easier to port Darwin to a SMT processor in which its "threads" were light weight or full fledged? Or both equally well? Thanks, Bernie PS I'm really happy Apple decided to finally follow the dual processor route. (It is about time! :-) _______________________________________________ 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.