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Xref: sserve comp.os.os2.programmer.misc:9717 comp.os.linux.development:8872 comp.os.minix:23713 comp.os.mach:3787 comp.periphs:5465 comp.unix.bsd:13914 comp.unix.pc-clone.32bit:6225 comp.os.386bsd.development:2084 comp.sys.ibm.pc.hardware.misc:5171 Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!bunyip.cc.uq.oz.au!munnari.oz.au!spool.mu.edu!agate!library.ucla.edu!psgrain!reuter.cse.ogi.edu!netnews.nwnet.net!news.u.washington.edu!tzs From: tzs@u.washington.edu (Tim Smith) Newsgroups: comp.os.os2.programmer.misc,comp.os.linux.development,comp.os.minix,comp.os.mach,comp.periphs,comp.unix.bsd,comp.unix.pc-clone.32bit,comp.os.386bsd.development,comp.sys.ibm.pc.hardware.misc Subject: Re: [Announcement] 386BSD Release 1.0 Date: 8 May 1994 05:23:50 GMT Organization: University of Washington School of Law, Class of '95 Lines: 27 Message-ID: <2qht16$msc@news.u.washington.edu> References: <2q63q2$927@dearg.cuillin.org.uk> <hastyCpCLny.5q8@netcom.com> <newcombe.142.00141E4A@aa.csc.peachnet.edu> <2qdvvp$r@bmerha64.bnr.ca> NNTP-Posting-Host: stein.u.washington.edu In article <2qdvvp$r@bmerha64.bnr.ca>, Jean Cyr <jcyr@bnr.ca> wrote: >Can't be done. The initial boot stage (reading the boot sector and jumping >to it) is handled by your machine's BIOS rom. Currently all BIOS that I've >seen look for boot sectors on floppy and hard disk. They never look for CD. >How could they ? There's no BIOS support for CD. You seem to think BIOS ROMs come with the machine. That's only partly correct. They also come with adaptor cards. Early on in system initialization, the BIOS that comes with the motherboard scans the ROM address space looking for BIOS ROMs on adaptor cards. Each such ROM found is called to initialize itself. The BIOS ROM on a SCSI card typically at this point scans the SCSI bus, and if it finds any bootable hard disks, installs INT 13h handlers for them. It would be trivial for such a BIOS to make a CD-ROM that contains a bootable disk image appear to be a read-only hard disk on INT 13h drive 0x80. The system would then boot from it. Heck, if the people who wrote the host adaptor firmware wanted to, they could support booting from a scanner... I wrote a SCSI BIOS that doesn't support booting from a CD-ROM, because it never occurred to me or the people we wrote it for that this would be a cool thing, but if it had, it would have taken about 5 minutes to modify the BIOS to support it. It doesn't surprise me to find that someone did think of it and do it. It really is trivial. --Tim Smith