From owner-freebsd-current@FreeBSD.ORG Wed Nov 24 14:28:58 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 2614216A4CE for ; Wed, 24 Nov 2004 14:28:58 +0000 (GMT) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9A35143D1F for ; Wed, 24 Nov 2004 14:28:57 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from [192.168.1.250] (pool-68-161-115-118.ny325.east.verizon.net [68.161.115.118]) by pi.codefab.com (8.12.11/8.12.11) with ESMTP id iAOESbhC014573 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 24 Nov 2004 09:28:39 -0500 (EST) Message-ID: <41A49A7B.6020009@mac.com> Date: Wed, 24 Nov 2004 09:28:11 -0500 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.3) Gecko/20040910 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "M. Warner Losh" References: <200411231343.22760.jhb@FreeBSD.org> <20041124002603.GD20881@squash.dsto.defence.gov.au> <41A416E7.4030107@mac.com> <20041123.235250.118899687.imp@bsdimp.com> In-Reply-To: <20041123.235250.118899687.imp@bsdimp.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=-4.5 required=5.5 tests=AWL,BAYES_00 autolearn=ham version=2.64 X-Spam-Checker-Version: SpamAssassin 2.64 (2004-01-11) on pi.codefab.com 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 14:28:58 -0000 M. Warner Losh wrote: > In message: <41A416E7.4030107@mac.com> > Chuck Swiger writes: [ ... ] > : 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. > : > : A PCI-PCI bridge is commonly found on multifunction PCI cards, an example > : would be the DEC 21151 chip found on various four-port NICs. > > Newer laptops (and other machines) typically have a PCI PCI bridge > that all the builtin hardware lives behind. Many, but not all, of > these bridges are transparent pci pci bridges, maning they act much > like a subtractively decoded bridge. You are absolutely right; the impression I got was that laptops like to have PCI-PCI bridges in order to make it easier to route interrupts for devices on a docking station or the like. If they don't use such a PCI-PCI bridge chip, then the laptop's BIOS needs to set up a $PIR table which routes interrupts properly for _all_ of the possible docking station configurations and devices to which the laptop might be attached to. Making things work right with a known configuration seems to be hard enough for some vendors, so it's not surprising that pre-planning for possible future configurations is difficult to do without using a PCI-PCI bridge to aggregate the devices lurking behind it. -- -Chuck