From owner-freebsd-questions Mon Apr 5 20:33:21 1999 Delivered-To: freebsd-questions@freebsd.org Received: from hades.riverstyx.net (hades.riverstyx.net [216.94.42.239]) by hub.freebsd.org (Postfix) with ESMTP id E58CF14CAE for ; Mon, 5 Apr 1999 20:32:35 -0700 (PDT) (envelope-from unknown@riverstyx.net) Received: from localhost (unknown@localhost) by hades.riverstyx.net (8.9.3/8.9.3) with ESMTP id TAA23543; Mon, 5 Apr 1999 19:32:40 -0700 Date: Mon, 5 Apr 1999 19:32:40 -0700 (PDT) From: To: "Dragon Knight ][" Cc: FreeBSD Questions Subject: Re: K6-2/333, was: Re: Debug kernel by default (was: System sizewith -g) In-Reply-To: <37097B00.2186EB92@dtgnet.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Presumably the logic here is that it eliminates wait-states while the two busses sync. If everything's running on the same base with different multipliers it's easier. 33*2=66, so it's either a go, or wait one cycle. With 100/66/33, and you're trying to move data between a 66 bus and a 100 bus at any random moment, it's either a go (1/3 of the time), wait one cycle (1/3 of the time), or wait 2 cycles (1/3 of the time). WARNING: cheesy ascii art approaching! a) |----------|---------| 2 5 b) |-------|------|-----| 1 3 4 at position one, you must wait 2 cycles before you're in sync again. at 3, you wait one cycle. at 4, you don't wait. average is 1 cycle wasted waiting. that's if your 100 wants to send. when the other side's picking the moment, you're waiting 1 cycle at position 2, and not waiting at 5. if you have just 33/66, the most you'll ever have to wait is one cycle before both are in sync. that means only 1/2 cycle wasted on average. statistically, it's better. i'm just flailing here, if anyone can correct me, please do. this is just cute math, i don't know how it would actually work. --- tani hosokawa river styx internet On Mon, 5 Apr 1999, Dragon Knight ][ 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. > > > Samuel Greear > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message