From owner-freebsd-hackers Wed Mar 22 20:19:15 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id UAA28168 for hackers-outgoing; Wed, 22 Mar 1995 20:19:15 -0800 Received: from gndrsh.aac.dev.com (gndrsh.aac.dev.com [198.145.92.241]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id UAA28160 for ; Wed, 22 Mar 1995 20:19:12 -0800 Received: (from rgrimes@localhost) by gndrsh.aac.dev.com (8.6.8/8.6.6) id UAA11500; Wed, 22 Mar 1995 20:18:49 -0800 From: "Rodney W. Grimes" Message-Id: <199503230418.UAA11500@gndrsh.aac.dev.com> Subject: Re: ata/ide sector translation modes c/h/s vs. LBA? To: PVinci@ix.netcom.com (Paul Vinciguerra) Date: Wed, 22 Mar 1995 20:18:49 -0800 (PST) Cc: hackers@FreeBSD.org In-Reply-To: <199503230344.TAA12714@ix2.ix.netcom.com> from "Paul Vinciguerra" at Mar 22, 95 07:44:36 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Content-Length: 1019 Sender: hackers-owner@FreeBSD.org Precedence: bulk > > I know you all must now be tired of all the ATA questions, but ... > > Why does the ATA standard make such a big stink about LBA mode?? Because it is *new*, and allows you to use drives >536870912 bytes. > As I see it, either way, you have to translate either mode into: > > Sector Number > Cylinder Low > Cylinder High > Dev/Head > > So, how does LBA mode improve performance -- isn't it just a different > set of calculations that need be done before *Each* command?? Am I > missing something? It greatly simplifies the calculation for this. Basically a drive in LBA mode has 256 sectors, 16 heads and upto 1024 cylinders. The bios can then simply use OR and SHIFT to get a logical block number. I am leaving out lots of details, I have not yet unassembled awards LBA code so I am not sure of all the details, but that is the just of it. -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Custom computers for FreeBSD