From owner-freebsd-current@FreeBSD.ORG Wed Nov 24 21:19:20 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 B5F1816A4CE; Wed, 24 Nov 2004 21:19:20 +0000 (GMT) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4BBCE43D5A; Wed, 24 Nov 2004 21:19:20 +0000 (GMT) (envelope-from scottl@freebsd.org) Received: from [192.168.254.11] (junior-wifi.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.12.11/8.12.10) with ESMTP id iAOLMHMs065225; Wed, 24 Nov 2004 14:22:18 -0700 (MST) (envelope-from scottl@freebsd.org) Message-ID: <41A4FAF9.1080704@freebsd.org> Date: Wed, 24 Nov 2004 14:19:53 -0700 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.2) Gecko/20040929 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Charles Swiger References: <200411231226.38172.jkim@niksun.com> <41A49312.5@freebsd.org> <41A49EF1.8030603@mac.com> <200411241019.25271.jhb@FreeBSD.org> <0F179BC4-3E3E-11D9-BD47-003065ABFD92@mac.com> In-Reply-To: <0F179BC4-3E3E-11D9-BD47-003065ABFD92@mac.com> X-Enigmail-Version: 0.86.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, hits=0.0 required=3.8 tests=none autolearn=no version=2.63 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on pooker.samsco.org cc: freebsd-current@freebsd.org 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 21:19:20 -0000 Charles Swiger wrote: > On Nov 24, 2004, at 10:19 AM, John Baldwin wrote: > >>> 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 is the host-pci bridge. It contains a virtual PCI-PCI >> bridge/bus that represents AGP. > > > Agreed, although AGP is something of a special case. > >> The chipset uses a propietary interconnect to the southbridge... > > > Such as VIA's V-link. > >> ...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. > > > You and Scott are correct. pciconf claims that something like a 440BX > northbridge (82443BX) contains both a HOST-PCI and a PCI-PCI bridge, > whereas the PIIX4 southbridge (82371AB) has a PCI-ISA bridge, as well as > ATA and the other things I'd mentioned. > > I apologize if I confused the person I was trying to answer. > Not a problem. The V-Link and ICH buses are really just high-speed tunnels for PCI. Before their invention, the southbridge was directly connected to the northbridge via PCI. Scott