From owner-freebsd-questions@FreeBSD.ORG Wed Sep 6 18:55:21 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C24AD16A4DA for ; Wed, 6 Sep 2006 18:55:21 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from smtpout.mac.com (smtpout.mac.com [17.250.248.176]) by mx1.FreeBSD.org (Postfix) with ESMTP id 313D043D4C for ; Wed, 6 Sep 2006 18:55:21 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from mac.com (smtpin03-en2 [10.13.10.148]) by smtpout.mac.com (Xserve/8.12.11/smtpout06/MantshX 4.0) with ESMTP id k86ItKpk014282; Wed, 6 Sep 2006 11:55:20 -0700 (PDT) Received: from [17.214.13.96] (a17-214-13-96.apple.com [17.214.13.96]) (authenticated bits=0) by mac.com (Xserve/smtpin03/MantshX 4.0) with ESMTP id k86ItHJb001481; Wed, 6 Sep 2006 11:55:19 -0700 (PDT) In-Reply-To: <890E919AB0857D4A8A52A4AD5E0F0F6221A1C1@msc-server.msc.mcgregor-surmount.com> References: <890E919AB0857D4A8A52A4AD5E0F0F6221A1C1@msc-server.msc.mcgregor-surmount.com> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <91AFEF09-05EE-41BE-846F-665FBE64EE06@mac.com> Content-Transfer-Encoding: 7bit From: Chuck Swiger Date: Wed, 6 Sep 2006 11:55:17 -0700 To: "Hilt, Ian" X-Mailer: Apple Mail (2.752.2) X-Brightmail-Tracker: AAAAAQAAA+k= X-Language-Identified: TRUE Cc: freebsd-questions@freebsd.org Subject: Re: Origin of hard drive parameters X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Sep 2006 18:55:21 -0000 On Sep 6, 2006, at 11:40 AM, Hilt, Ian wrote: > Basically, I want to know where the BIOS gets the hard drive > parameters > when the Drive Type is set to "AUTO" in the BIOS configuration. The > best > I've been able to come up with from the internet is an "IDENTIFY" > command that purportedly > () gets its > information from the "IDE controller". This does not answer my > question > completely. Are the parameters returned by the controller hard coded > into a chip on the board or are they on the platters of the hard > drive, > or neither? "Neither" is probably the best answer. The hard disk has an on-board controller which answers the ATA "IDENTIFY DEVICE" command with the hard drive parameters used by the BIOS, assuming that the BIOS is operating in the legacy C/H/S mode rather than the newer LBA mode which uses absolute block numbers. Note that the answer the drive controller gives will normally be a fabricated geometry which does not have anything to do with the actual geometry of the physical device, in part because drives nowadays keep a variable number of sectors per track rather than using a CAV layout. -- -Chuck