Date: Mon, 20 Nov 2000 14:32:39 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> Cc: stable@FreeBSD.org, rnordier@FreeBSD.org Subject: Re: Dedicated disks (was: Dangerously Dedicated) Message-ID: <XFMail.001120143239.jhb@FreeBSD.org> In-Reply-To: <200011202157.NAA19653@gndrsh.dnsmgr.net>
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On 20-Nov-00 Rodney W. Grimes wrote: >> Greg Lehey wrote: >> >> > > Why do you *insist* on calling it a "Microsoft partition table"?? >> > >> > Hmm. I was going to say "Because it was introduced with Microsoft >> > 2.0", but I'm no longer so sure. Reading the MS-DOS 2.11 source code, >> > it seems that they didn't have a partition table at the time. >> >> Of course they had a partition table at the time, and of course >> MS-DOS 2.11 used it: >> >> [io.sys] >> 1431 8d9fbe01 lea bx,[bx+0x1be] >> 1435 8b4740 mov ax,[bx+0x40] >> 1438 3d55aa cmp ax,0xaa55 >> 143b 7539 jnz 0x1476 >> 143d b90400 mov cx,0x4 >> 1440 807f0401 cmp byte [bx+0x4],0x1 >> 1444 7407 jz 0x144d >> 1446 83c310 add bx,byte +0x10 >> 1449 e2f5 loop 0x1440 >> 144b eb29 jmp short 0x1476 > > Thank you for digging this out, it saved me the time. This goes to show > that infact the FUD in this whole discussion is that the partition table > is handled by the BIOS. The above code validates the signature and finds > the active partition in the MBR. (There is similiar code in the MS and PC > DOS MBR code to find boot1, but again this is the MBR code, NOT THE BIOS). > > Let me state this one more time loudly for those calling themselves boot > code experts. THE PARTITION TABLE IN THE MBR IS NOT DEALT WITH BY THE BIOS, > BIOSES THAT TRY TO MAKE HEADS OR TALES OF PARTITION TABLES ARE TECHNICALLY > BROKEN AND VIOLATE IBM AT COMPATIBILITY. If you doubt this go read about > BIOS service 19H, IPL load. Go rewrite Adaptec's SCSI firmware and replace all the b0rked BIOS's out in the field. Then come back with a productive answer. Thank you. I really wish you would go read all the archives for the actual real world issues. The PC arch has changed and acquired new 'de facto' standards since 1980. -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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