From owner-freebsd-bugs Wed Aug 21 15:10:17 2002 Delivered-To: freebsd-bugs@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C32CE37B400 for ; Wed, 21 Aug 2002 15:10:15 -0700 (PDT) Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id 392C243E65 for ; Wed, 21 Aug 2002 15:10:14 -0700 (PDT) (envelope-from bde@zeta.org.au) Received: from bde.zeta.org.au (bde.zeta.org.au [203.2.228.102]) by mailman.zeta.org.au (8.9.3/8.8.7) with ESMTP id WAA05445; Wed, 21 Aug 2002 22:09:56 GMT Date: Thu, 22 Aug 2002 08:16:22 +1000 (EST) From: Bruce Evans X-X-Sender: bde@gamplex.bde.org To: "Simon 'corecode' Schubert" Cc: swp@uni-altai.ru, Subject: Re: boot1.s In-Reply-To: <20020821131613.115c0553.corecode@corecode.ath.cx> Message-ID: <20020822081252.H461-100000@gamplex.bde.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-bugs@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Wed, 21 Aug 2002, Simon 'corecode' Schubert wrote: > On Wed, 21 Aug 2002 11:34:29 +0700 mitrohin a.s. wrote: > > > file /usr/src/sys/boot/i386/boot2/boot1.s, line 140 > > > > mov $part4,%si # Partition > > what %dl have value? i don`t seen initialization for %dl/%dx. bug? > > no. that's set by the BIOS. > > > cmpb $0x80,%dl # Hard drive? > > jb main.4 # No Except some BIOSes are broken. boot1.s trusts %dl if it is >= 0x80 (which should mean a hard drive), but not otherwise. It assumes that values between 1 and 0x7f inclusive mean a broken BIOS and replaces them by 1. Thus booting from floppy drives other the first one (according to the BIOS's numbering) cannot work. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message