Date: Thu, 22 Aug 2002 08:16:22 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: "Simon 'corecode' Schubert" <corecode@corecode.ath.cx> Cc: swp@uni-altai.ru, <freebsd-bugs@FreeBSD.ORG> Subject: Re: boot1.s Message-ID: <20020822081252.H461-100000@gamplex.bde.org> In-Reply-To: <20020821131613.115c0553.corecode@corecode.ath.cx>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20020822081252.H461-100000>