From owner-freebsd-current@FreeBSD.ORG Wed Nov 24 17:27:07 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 DA6B316A4CE; Wed, 24 Nov 2004 17:27:07 +0000 (GMT) Received: from smtpout.mac.com (smtpout.mac.com [17.250.248.45]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7E0BC43D45; Wed, 24 Nov 2004 17:27:07 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from mac.com (smtpin01-en2 [10.13.10.146]) by smtpout.mac.com (Xserve/MantshX 2.0) with ESMTP id iAOHR6Xg010037; Wed, 24 Nov 2004 09:27:07 -0800 (PST) Received: from [10.1.1.245] (nfw2.codefab.com [199.103.21.225] (may be forged)) (authenticated bits=0)iAOHR5cK004798; Wed, 24 Nov 2004 09:27:06 -0800 (PST) In-Reply-To: <200411241019.25271.jhb@FreeBSD.org> References: <200411231226.38172.jkim@niksun.com> <41A49312.5@freebsd.org> <41A49EF1.8030603@mac.com> <200411241019.25271.jhb@FreeBSD.org> Mime-Version: 1.0 (Apple Message framework v619) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: <0F179BC4-3E3E-11D9-BD47-003065ABFD92@mac.com> Content-Transfer-Encoding: 7bit From: Charles Swiger Date: Wed, 24 Nov 2004 12:27:04 -0500 To: John Baldwin X-Mailer: Apple Mail (2.619) cc: freebsd-current@FreeBSD.org 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 17:27:08 -0000 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. -- -Chuck