From owner-freebsd-hackers Wed Mar 22 22:48:51 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id WAA01406 for hackers-outgoing; Wed, 22 Mar 1995 22:48:51 -0800 Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.34]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id WAA01399 for ; Wed, 22 Mar 1995 22:48:35 -0800 Received: (from bde@localhost) by godzilla.zeta.org.au (8.6.9/8.6.9) id QAA04580; Thu, 23 Mar 1995 16:47:34 +1000 Date: Thu, 23 Mar 1995 16:47:34 +1000 From: Bruce Evans Message-Id: <199503230647.QAA04580@godzilla.zeta.org.au> To: PVinci@ix.netcom.com, rgrimes@gndrsh.aac.dev.com Subject: Re: ata/ide sector translation modes c/h/s vs. LBA? Cc: hackers@FreeBSD.org Sender: hackers-owner@FreeBSD.org Precedence: bulk >> 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. No. Even the old ATA standard specifies addressing drives with 65535(+1?) * 16 * 255 sectors (almost 128GB). LBA only increases the limit to 65536 * 16 * 256. See "Yet Another ATA-2/Fast-ATA/EIDE FAQ" in comp.sys.ibm.pc.hardware.storage. >It greatly simplifies the calculation for this. Basically a drive ^slightly >in LBA mode has 256 sectors, 16 heads and upto 1024 cylinders. Up to 65536 or 65536 cylinders. Oops, in previous mail I said that LBA addresses are 24 bits. They are actually 28 bits (4 more in the old head bits). The bits are rearranged (the head bits become bits 24-27 of the LBA, and the braindamaged 1-based sector numbers are gone), so it is only a heuristic to think of the translation as giving a 256S * 16H geometry. Bruce