Date: Wed, 7 Apr 1999 02:54:33 +0100 From: Mark Ovens <marko@uk.radan.com> To: Darren Pilgrim <dpilgrim@uswest.net> Cc: "Dragon Knight ][" <dragonknight@dtgnet.com>, FreeBSD Questions <questions@freebsd.org> Subject: Re: K6-2/333, was: Re: Debug kernel by default (was: System sizewith -g) Message-ID: <19990407025433.C4453@marder-1.localhost> In-Reply-To: <3709EDEB.BE17A2E8@uswest.net>; from Darren Pilgrim on Tue, Apr 06, 1999 at 04:20:11AM -0700 References: <Pine.LNX.4.04.9904051605450.10244-100000@hades.riverstyx.net> <3709569A.70EEC38A@uswest.net> <37097B00.2186EB92@dtgnet.com> <3709EDEB.BE17A2E8@uswest.net>
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On Tue, Apr 06, 1999 at 04:20:11AM -0700, Darren Pilgrim wrote:
> "Dragon Knight ][" wrote:
> > Darren Pilgrim wrote:
> <snip>
> > > While this is mathematically and theoretically sound thinking, tests
> > > have shown that there is little CPU/memory performance gain with a
> > > 100MHz bus. Just take a look at www.tomshardware.com. As for my own
> > > systems, I run K6-2 333s at 5x66 just because it sets the PCI and AGP
> > > clocks at their spec'd rate of 33 and 66MHz, respectively, while
> > > providing the CPU's spec'd 333MHz.
> > >
> >
> > As you say, there is a little CPU/Memory performance increase at 100MHz fsb.
> > So I do not see your logic in setting your chips at 5x66 because it puts your
> > PCI and AGP where they should be. One of the 'specs' of the 100MHz fsb is
> > that PCI and AGP cards will run at their normal speed of 33 and 66MH. I believe
> > this is also true of the 95MHz busses.
>
> Actually I said "there is little", I didn't put an "a" in there. Plus
> the only performance increases I've ever seen are on stress-test
> benchmarks where the disk, memory, and video are all in use at once.
> This situation is purely for performance testing, there's is no real-
> world application.
>
> 95MHz produces slower AGP/PCI clocks and, lacking a performance gain
> with a faster FSB, using 66MHz to get faster AGP/PCI clocks makes more
> sense if your CPU isn't rated for a 100MHz multiple. This is just
> splitting hairs; IRL, a <4MHz clock difference is nothing performance
> wise. Your cards might complain about it though. Particularly the
> ones that rely on the bus-clock for their internal clocks, like some
> sound and video cards.
>
As the person who effectively started all this discussion about
bus speeds and multipliers I just want to thank all the contributors
to this thread. I now have a better understanding of how it all
works. The fundamental misunderstanding I had was that the CPU
itself did the mutliplication and that the m/b jumpers simply "told"
the CPU what multiple of the bus speed to use.
I guess that AMD only state 95MHz & 3.5X, and not 66MHz & 5X,
because it gives the maximum absolute performance of the chip as
the CPU <==> memory is running at its highest speed.
> --
> dpilgrim@uswest.net /\ / __ Our lies are merely the
> gryph@mindless.com / \/OC/URNE truth of another world
> ICQ: 29880099 Death is not a kill -9, just a
> DALnet: anim0s make world and shutdown -r now PGPKey available
>
>
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_______________________________________________________________
Mark Ovens, CNC Apps Engineer, Radan Computational Ltd. Bath UK
CAD/CAM solutions for Sheetmetal Working Industry
mailto:marko@uk.radan.com http://www.radan.com
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