Date: Thu, 06 Apr 2000 14:08:17 -0700 From: Kent Stewart <kstewart@3-cities.com> To: R Joseph Wright <rjoseph@speakeasy.org> Cc: Alfred Perlstein <bright@wintelcom.net>, freebsd-questions@FreeBSD.ORG Subject: Re: smp motherboards/concepts Message-ID: <38ECFCC1.885085E9@3-cities.com> References: <Pine.BSF.4.21.0004061326390.38754-100000@mammalia.sea>
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R Joseph Wright wrote: > > On Thu, 6 Apr 2000, Alfred Perlstein wrote: > > > * R Joseph Wright <rjoseph@speakeasy.org> [000406 12:07] wrote: > > > I know FreeBSD supports multiple processors, but how many? What > > > motherboard(s) support more than two, for example using a pentium pro? > > > > People have been known to use FreeBSD in quad processor systems. > > > > > > > > Is the concept of SMP similar to beowulf clusters? I've read a little > > > about those, and as I understand, simply clustering many computers together > > > does not guarantee a faster system, if the software is not especially > > > compiled to handle it. Is this also true of SMP? I'm specifically > > > thinking of using an SMP system for doing raytracing. > > > > The SMP you get with FreeBSD would be multiple processors in a single > > system, unless you can break down your raytracing application into > > multiple processes to act on different threads at the same time you > > won't see any improvement. > > Is it only useful for running many applications at the same time? This isn't really true. It is entirely based on how smart your compiler is. The compilers I used to use on the Cray at work were really smart this way. They were also really slow. What it would do is send something like each loop of your typical for-loop to a different cpu. In the case of a typical YM/P, you had 16 cpu's and would chunk through the loop in increments of 16. The thing was each loop had to be independant of the others. That is where the smarts were required. A 486 using Lehey or Ryan McFarland Fortran could compile a program faster on a 486, which didn't do SMP. Shell commands such as pipes were also lucky recipients of the benefits of SMP. Each piped command would be running on a different cpu if a different cpu was available. This was multi-processing at the command line. A Cray class on performance spent the first morning introducing you to your muli-processing hardware. If you didn't understand that, you didn't stand a chance of making your program run well in the SMP environment. If your situation doesn't fit any of the above, then, the many applications rule applies. Kent > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message -- Kent Stewart Richland, WA mailto:kstewart@3-cities.com http://www.3-cities.com/~kstewart/index.html FreeBSD News http://daily.daemonnews.org/ SETI(Search for Extraterrestrial Intelligence) @ HOME http://setiathome.ssl.berkeley.edu/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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