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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!simtel!news.kei.com!world!mv!news.NH.Destek.Net!cherkus From: cherkus@unimaster.com (Dave Cherkus) Newsgroups: comp.sys.ibm.pc.hardware.chips,comp.sys.ibm.pc.hardware.systems,comp.os.linux.hardware,comp.unix.bsd.freebsd.misc Subject: Re: Dual Pentium MotherBoard. Followup-To: comp.sys.ibm.pc.hardware.chips,comp.sys.ibm.pc.hardware.systems,comp.os.linux.hardware,comp.unix.bsd.freebsd.misc Date: 29 Sep 1995 16:17:43 GMT Organization: The Destek Group, Inc. Lines: 61 Message-ID: <44h677$kda@synergy.Destek.Net> References: <44735j$7qo@kappa.usc.edu> <DFHG2v.7Mw@ritz.mordor.com> <4491rp$gb0@mozo.cc.purdue.edu> <DFKIA4.AL0@undergrad.math.uwaterloo.ca> NNTP-Posting-Host: fastball.unimaster.com X-Newsreader: TIN [version 1.2 PL2] Xref: euryale.cc.adfa.oz.au comp.sys.ibm.pc.hardware.chips:34701 comp.sys.ibm.pc.hardware.systems:20607 comp.os.linux.hardware:17409 comp.unix.bsd.freebsd.misc:6901 Carsten Whimster (bcrwhims@undergrad.math.uwaterloo.ca) wrote: : In article <4491rp$gb0@mozo.cc.purdue.edu>, : Chien-hung Lin <lin1974@expert.cc.purdue.edu> wrote: : | In article <DFHG2v.7Mw@ritz.mordor.com>, : | Chris Mauritz <ritz@ritz.mordor.com> wrote: : | >Free/NetBSD/Linux won't take advantage of the extra cpu. : | : | What systems or OS or programs would take advantage of the extra : | CPU? Would it need a driver to run the extra CPU, if so how much memory : | would it take up? : The O/S has to support it, and I have never heard of a driver being : able to do this on its own. There are two types of (common) systems, : from what I hear: each CPU has its own memory and cache ($), each CPU : shares the memory and/or cache. There are some of both on the market. While I might not need to say this, the designs that share cache don't work very well because the cache is accessed so frequently. As for memory demands, the code and data added to the system doesn't increase the memory demand much (although true SMP does add tremendously to the complexity of that code!). What does increase the memory use is that the system can now do a lot more work per unit time and this usually means that it can touch a lot more memory per unit time. If you want the speed increase you are paying for by buying the second cpu, you should think about buying more memory. Think about a car that can now go twice as fast. It should cover twice as much road per unit time, unless of course it does a lot of looping around. : | In addition, how much performance would one expect to see w/ the extra CPU, : | would I need 2 CPU fans instead of one? : IBM says that with OS/2 SMP and a well threaded program, the benefits : are up to nearly 100%, but with a single threaded program, the : benefits would be much lower, maybe 25%, and this benefit is only : realized because the O/S can run on a separate CPU. It really varies a : lot. Assuming good hardware, of course... As for emphasis on threading the programs, it is surely recommended, but on multitasking systems different programs (tasks) can run on different CPUs so you can see a win for SMP with single threaded apps. The degree to which this happens is dependent on what you want to do with your system. It's easy for a server to have lots of things to do at one time, each in seperate tasks. Desktops also can benefit. You can use a parallel 'make' program that will compile different targets on different processors. You can download new screensaver fodder while you type e int hat documetn, etc. etc. etc. An excellent text on SMP and other interesting stuff is 'UNIX Systems for Modern Architectures', by Curt Schimmel. Of course it's UNIX specific, but the text is well written and describes many attributes of modern systems so I think you can get a lot out of it even if you are not into UNIX. Usual disclaimers etc. -- Dave Cherkus ----- UniMaster, Inc. ----- Contract Software Development Specialties: UNIX Internals TCP/IP OSF/1 AlphaAXP AIX Performance ISDN Email: cherkus@UniMaster.COM Tel: (603) 888-8308 Fax: (603) 888-4598 Live Free or Die - New Hampshire has 3 seasons: ice, mud and black fly