From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.33) id 1BlkSW-0005xz-KC for qemu-devel@nongnu.org; Sat, 17 Jul 2004 04:22:16 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.33) id 1BlkSU-0005xU-Ly for qemu-devel@nongnu.org; Sat, 17 Jul 2004 04:22:16 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.33) id 1BlkSU-0005xR-Dr for qemu-devel@nongnu.org; Sat, 17 Jul 2004 04:22:14 -0400 Received: from [80.59.103.181] (helo=claunia.com) by monty-python.gnu.org with esmtp (TLSv1:DES-CBC3-SHA:168) (Exim 4.34) id 1BlkPP-0007Za-6B for qemu-devel@nongnu.org; Sat, 17 Jul 2004 04:19:11 -0400 From: "Natalia Portillo" Subject: RE: [Qemu-devel] BIOS behaves different as real BIOS Date: Sat, 17 Jul 2004 09:20:05 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable In-Reply-To: <1090048364.21480.6.camel@pcgem.rdg.cyberkinetica.com> Message-Id: Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Well the PC-DOS 1.0 does not have that signature, and also does not = create it in any disk you format. Nor the SCO Xenix has it. I know this signature is present on DOS 3.0 and upper versions in all = disks you create. I not know about DOS 2.0 (I lost my copy of this version). > -----Mensaje original----- > De: qemu-devel-bounces+iosglpgc=3Dteleline.es@nongnu.org > [mailto:qemu-devel-bounces+iosglpgc=3Dteleline.es@nongnu.org] > En nombre de Antony T Curtis > Enviado el: s=E1bado, 17 de julio de 2004 8:13 > Para: qemu-devel@nongnu.org > Asunto: Re: [Qemu-devel] BIOS behaves different as real BIOS >=20 > On Sat, 2004-07-17 at 07:01, Natalia Portillo wrote: > > Hi! > >=20 > > I tried to boot an old operating system from qemu and I get > a message > > from BIOS saying that tbe floppy is not bootable > (literally: "FATAL:=20 > > Not a bootable disk"). > >=20 > > I think that this is because the BIOS searches for the 0x55AA=20 > > signature on last two bytes of first sector of disk. > > As far as I remember, this signature was introduced very > lately and as > > far as I tested on my real systems, this signature is not really=20 > > searched at boot time, and every DOS before 3.0 doesn't > have it (it is > > used also by later DOSes and Windows to identify a FAT > filesystem), at > > least on floppies (I think that on hard disks it is also > ignored, but > > never tested -0x55AA is also used to identify Intel > partition scheme, aka MBR-). >=20 > I remember looking at the IBM PC/XT BIOS source and seeing it, and=20 > when I used to play with putting my own messages in the boot sector,=20 > It had to be there. This was around 15 years ago. The old IBM PC/XT=20 > would boot into ROM Cassette BASIC if it did not find the signature.=20 > It is possible that the original IBM PC did not have the check but by=20 > the time the PC/XT came out, it did. The model of the PC/XT I had was=20 > 5150 (the 2 full height floppy drive model) >=20 > >=20 > -- > Antony T Curtis >=20 >=20 >=20 > _______________________________________________ > Qemu-devel mailing list > Qemu-devel@nongnu.org > http://lists.nongnu.org/mailman/listinfo/qemu-devel