Date: Sat, 10 May 1997 15:13:55 +0000 From: "Riley J. McIntire" <chaos@mail.tgci.com> To: Michael Alwan <alwan@rma.edu> Cc: questions@FreeBSD.ORG Subject: Re: advantages of symmetric processing Message-ID: <199705102241.PAA21385@train.tgci.com>
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> Date: Sat, 10 May 1997 17:25:46 -0400 > To: questions@FreeBSD.ORG > From: Michael Alwan <alwan@rma.edu> > Subject: advantages of symmetric processing > To anyone interested: [snip] > On the other hand, there are other socket 7 processors like the AMD K6 with > all the 32 bit optimizations, faster clock speeds, and lower prices than > newer Intel stuff. The upgrade path (beyond 266 MHZ) seems unpredictable, > and as far as I know, it can't be multiprocessed. Sure it can with the appropriate motherboard. > > Here's my question. All other things being equal (version of operating > system, system bus speed, amount of ram, kernel configuration, disk speed, > etc.) which runs a given app faster--symmetric multiprocessing or faster > clock speeds with one processor? All things being equal, if you double your clock speed you will double your on-chip processing capability. Your on board i/o capacity stays the same. If you double your processor, you may or may not double your processing capability. Assuming you're looking to increase the performance of a single application, as opposed to increasing performance of a system running multiple applications (or instances of same), the application must be written to take advantage of SMP. Assuming such an application, it *may* also take better advantage of disk i/o and memory i/o. Maybe. > Compare, say, two 120 MHZ Pentiums to one 200 MHZ Pentium Pro. Do > something CPU-intensive in a database. Which will come out ahead? What is > the break-even point? I'm less likely to be networking or using my machine > as a server and more likely to be image-processing or DTP or using a database. Depends on the database ( or app) and what you're doing with it. A single threaded app will run faster on the 200 Mhz PPro. A multi-threaded app *might* take better advantage of the 2-120s, although you are comparing apples and oranges. The PPro can really scream with certain apps. > > I haven't been researching this for long, but everything I've read seems to > suggest adding a second processor doesn't increase the speed of a given > operation more than 50%. There is a lot more information about the impact > of cpu clock speeds, obviously because most people have one cpu. I also > realize that at the rate new hardware and software is coming out, any > prediction now might make no sense in 2 months. I'm just looking for the > most bang for the bucks I have now. > > If anyone has any answers experience, or opinions, I'd be really > interested. It's hard to get a straight answer from a vendor. > > Thanks, > > Michael You really need to define what you want to do and what application you're using to do it with before you can get a real grasp of this question. Ciao, Riley
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