From owner-freebsd-current@FreeBSD.ORG Wed Nov 24 15:41:13 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id AC7B116A4CE for ; Wed, 24 Nov 2004 15:41:13 +0000 (GMT) Received: from mail1.speakeasy.net (mail1.speakeasy.net [216.254.0.201]) by mx1.FreeBSD.org (Postfix) with ESMTP id 67F1643D41 for ; Wed, 24 Nov 2004 15:41:13 +0000 (GMT) (envelope-from jhb@FreeBSD.org) Received: (qmail 24169 invoked from network); 24 Nov 2004 15:41:13 -0000 Received: from dsl027-160-063.atl1.dsl.speakeasy.net (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) encrypted SMTP for ; 24 Nov 2004 15:41:12 -0000 Received: from [10.50.41.235] (gw1.twc.weather.com [216.133.140.1]) (authenticated bits=0) by server.baldwin.cx (8.12.11/8.12.11) with ESMTP id iAOFf5WV043775; Wed, 24 Nov 2004 10:41:10 -0500 (EST) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: freebsd-current@FreeBSD.org Date: Wed, 24 Nov 2004 10:19:25 -0500 User-Agent: KMail/1.6.2 References: <200411231226.38172.jkim@niksun.com> <41A49312.5@freebsd.org> <41A49EF1.8030603@mac.com> In-Reply-To: <41A49EF1.8030603@mac.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200411241019.25271.jhb@FreeBSD.org> X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on server.baldwin.cx cc: Chuck Swiger cc: Scott Long Subject: Re: Transparent bridges (a. k. a. HUB-to-PCI bridges)? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Nov 2004 15:41:13 -0000 On Wednesday 24 November 2004 09:47 am, Chuck Swiger wrote: > Scott Long wrote: > > Chuck Swiger wrote: > > [ ... ] > > >> A host-PCI bridge is typically part of the "southbridge" chip of > >> modern motherboards; on Intel motherboards this is also called the ICH > >> chip, such as the 82801AA/BA/CA/etc. VIA Southbridges include the > >> VT8233/8235/8237/etc. > > > > Nope. The southbridge typically holds a PCI-ISA bridge. The host-pci > > bridge is usually found in the northbridge part of the chipset. The > > whole point it to bridge the CPU to one or more PCI buses. > > I've been wrong before, but please double-check diagrams like: > > http://www.intel.com/design/chipsets/850/pix/850_800.gif > http://www.viatech.com/en/products/chipsets/p4-series/pt880/ > > The "northbridge", or MCH, connects to the CPU, AGP, RAM, and the > southbridge. > > The "southbridge", or ICH, connects to PCI, ATA, USB, BIOS chip, and the > northbridge. Newer southbridge chips may add integrated LAN, > 1394/Firewire, integrated AC'97 audio, and such via external codec chips > like the VT6103 PHY. The northbridge is the host-pci bridge. It contains a virtual PCI-PCI bridge/bus that represents AGP. The chipset uses a propietary interconnect to the southbridge such that the devices the north and south bridges connect to show up as one pci bus (bus 0). You could build a system without a southbridge (just PCI-X bridges or some such) and it would still have a host-pci bridge. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org