Author: Matt Taylor
Date: 11:14:53 12/17/02
Go up one level in this thread
On December 17, 2002 at 13:42:45, Robert Hyatt wrote: >On December 17, 2002 at 11:51:29, Vincent Diepeveen wrote: > >>On December 17, 2002 at 11:33:53, Robert Hyatt wrote: >> >>>On December 17, 2002 at 11:25:10, Vincent Diepeveen wrote: >>> >>>>On December 17, 2002 at 10:58:51, Bob Durrett wrote: >>>> >>>> >>>>Indeed you are correctly seeing that DIEP, which runs well on >>>>cc-NUMA machines as well, is a very good program from intels >>>>perspective, because even a 'second' processor on each physical >>>>processor which runs slower will still give it a speedboost, >>>>where others simply slow down a lot when you do such toying. >>>> >>>>So where many programs which will be way slower when running at >>>>4 processes/threads at a 2 processor Xeon, the software is the >>>>weak chain. >>> >>>What program fits this description? Not mine... >> >>*many* programs Bob. Crafty and DIEP aren't the only thing on the planet >>which gets used by most people who need a dual to perform multithreading >>for them. And majority of them uses NT4 server, 2000 server or XP pro/server. >> > >Yes, but you paint with a broad brush and say many will be way slower" and I >can't find a single one. I have run crafty. I have run several parallel >programs for things like molecular modeling, a simulation, and _none_ do worse >with HT on than with HT off. Not a single one so far. Some do _far_ better >with SMT than Crafty. Some do about the same. But I haven't found a one yet >that does worse unless you take the known exception for two processes running >on one physical cpu while the other is idle. That will be fixed shortly in >linux, and is already fixed in windows .net > >>For sure not some non existing OS that is seeing the clear difference >>between physical and split processors! > >Windows .net is not "non-existing". > >I don't follow the linux development kernels but wouldn't be surprised if they >already have fixes being tested... He is technically right about Windows .NET not existing. Microsoft isn't selling it yet, or at least I am under that impression as they usually test software -before- they release. I hope. >>>>In case of DIEP the bottleneck is the hardware clearly. Even >>>>something working great on cc-NUMA doesn't profit too much from >>>>the SMT/HT junk from intel. >>>> >>>>Though it is a great sales argument, the hard facts (11.4% >>>>speedboost) are not lying. >>>> >>>>So they need to press 2 cpu's which results in a cpu price >>>>2 times higher *at least* than an AMD cpu, the result >>>>is that you win 11.4% in speed. >>> >>>What are you talking about? SMT doesn't "press 2 cpus". >> >>the size of a P4 processor is a lot bigger than the AMD core, that's >>explaining for a big part why P4 is so much more expensive than a K7. > >What does that have to do with SMT? Let me rephrase your question. "The Tampa Bay Buccaneers are 11-3. What does that have to do with anything?" The size doesn't offset the cost by $600. Profit margins do. -Matt
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