From owner-freebsd-questions Tue Apr 6 19:18:14 1999 Delivered-To: freebsd-questions@freebsd.org Received: from allegro.lemis.com (allegro.lemis.com [192.109.197.134]) by hub.freebsd.org (Postfix) with ESMTP id F3C1915686 for ; Tue, 6 Apr 1999 19:18:04 -0700 (PDT) (envelope-from grog@freebie.lemis.com) Received: from freebie.lemis.com (freebie.lemis.com [192.109.197.137]) by allegro.lemis.com (8.9.1/8.9.0) with ESMTP id LAA11778; Wed, 7 Apr 1999 11:46:03 +0930 (CST) Received: (from grog@localhost) by freebie.lemis.com (8.9.3/8.9.0) id LAA13078; Wed, 7 Apr 1999 11:46:02 +0930 (CST) Message-ID: <19990407114602.Z2142@lemis.com> Date: Wed, 7 Apr 1999 11:46:02 +0930 From: Greg Lehey To: Mark Ovens , Darren Pilgrim Cc: "Dragon Knight ][" , FreeBSD Questions Subject: Re: K6-2/333, was: Re: Debug kernel by default (was: System sizewith -g) References: <3709569A.70EEC38A@uswest.net> <37097B00.2186EB92@dtgnet.com> <3709EDEB.BE17A2E8@uswest.net> <19990407025433.C4453@marder-1.localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.93.2i In-Reply-To: <19990407025433.C4453@marder-1.localhost>; from Mark Ovens on Wed, Apr 07, 1999 at 02:54:33AM +0100 WWW-Home-Page: http://www.lemis.com/~grog Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-41-739-7062 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wednesday, 7 April 1999 at 2:54:33 +0100, Mark Ovens wrote: > On Tue, Apr 06, 1999 at 04:20:11AM -0700, Darren Pilgrim wrote: >> "Dragon Knight ][" wrote: >>> Darren Pilgrim wrote: >> >>>> 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. It does. But there are various parts of the CPU. The part which creates the CPU internal clock is just a bit of relatively simple hardwired logic. > 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. Correct. And in fact I'd guess that you could probably choose 100 MHz. I've been running this chip for over a week now, and it seems to be fine, so I suppose it's time to start experimenting with overclocking. Greg -- When replying to this message, please copy the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message