From owner-freebsd-hardware Mon Sep 21 13:47:45 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA01715 for freebsd-hardware-outgoing; Mon, 21 Sep 1998 13:47:45 -0700 (PDT) (envelope-from owner-freebsd-hardware@FreeBSD.ORG) Received: from laker.net (jet.laker.net [205.245.74.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id NAA01687 for ; Mon, 21 Sep 1998 13:47:36 -0700 (PDT) (envelope-from sfriedri@laker.net) Received: from nt (digital-pbi-124.laker.net [208.0.233.24]) by laker.net (8.9.0/8.9.LAKERNET.NO-SPAM.SPAMMERS.AND.RELAYS.WILL.BE.TRACKED.AND.PROSECUTED.) with SMTP id QAA17455; Mon, 21 Sep 1998 16:46:37 -0400 Message-Id: <199809212046.QAA17455@laker.net> From: "Steve Friedrich" To: "Mike Smith" Cc: "hardware@FreeBSD.ORG" , "Joe Gleason" , "spork" Date: Mon, 21 Sep 1998 16:46:29 -0400 Reply-To: "Steve Friedrich" X-Mailer: PMMail 98 Professional (2.01.1600) For Windows NT (4.0.1381;3) MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Subject: Re: SCSI card used at cdrom.com? Sender: owner-freebsd-hardware@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Mon, 21 Sep 1998 09:48:37 -0700, Mike Smith wrote: >> On Sun, 20 Sep 1998 23:16:54 -0700, Mike Smith wrote: >> >> >> Wont the PCI bus still run at it's 33mhz regardless of what the system bus >> >> is and therefor the system bus speed would have no effect on PCI devices? >> > >> >Generally correct, yes. >> >> Actually, the correct answer is NO. With the exception of some newer >> motherboards, the PCI clock is derived from the system bus speed. Some >> newer moboards de-couple the PCI clock from the system bus. One place >> to do a little reading is http://www.tomshardware.com/ > >This place is Overclocker Heaven. If you configure your board >correctly, you won't exceed the 33MHz PCI clock limit, and this >includes running 100MHz slot 1 processors. > I think you missed my real point though. I was trying to tell everyone that on most older moboards, the system bus speed determines the PCI bus speed. So if you have a 60MHz bus speed, you have a 30MHz PCI speed. And a 66MHz bus speed gives you a 33MHz PCI bus. This doesn't pose a problem for correctly designed PCI boards. But some newer moboards allow higher bus speeds, like 87, etc., that will yield PCI bus speeds in excess of the spec, causing problems with some PCI boards. These newer moboards were "caused" by overclockers, but it is quite common to support bus speeds higher than 66, and if that moboard doesn't have separate jumpers for the "front side bus", you will have a PCI bus overspec if you use a bus speed higher than 66. So it really affects us all, thanks to the overclockers. I'm an old hardware guy and I do not condone overclocking. It's really only worthwhile to someone willing to sacrifice system stability for performance. That pretty much restricts it to people playing games, or experimenting. It's definitely not for production machines. >> You'll want to research Front Side Bus. > >Thanks, I know more than I need or want to know about this already. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message