Message-ID: <005301c04062$9af82420$11fea8c0@dell>
From: "Ben A L Jemmett" <ben DOT jemmett AT ukonline DOT co DOT uk>
To: <opendos AT delorie DOT com>
References: <00b801c02814$cc72b3a0$0400000a AT alain-nb> <01d601c04023$ddf751e0$cb881004 AT dbcooper>
Subject: Re: DRDOS FDISK
Date: Fri, 27 Oct 2000 23:09:40 +0100
Organization: Jemmett Glover Software Development
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Reply-To: opendos AT delorie DOT com

> I am really baffled by all of the talk about DRDOS FDISK. The only thing
any
> FDISK does is make entries into the last 66 bytes of the very first sector
> of track zero on a hdd.
DR-DOS's FDISK does more - it'll format the partition as well.  However,
FDISKs generally also rewrite the MBR - MS-DOS needs FDISK /MBR to do that.

> > BTW, I lost the message with the information about what should be in
> > the OEM signature to be MS-DOS compatible. Can someone please
> > resend it to me?   :)
> In retrospec of this paragraph that I am replying to now, I am at a loss
as
> to WHAT signature you want.
The OEM label, found in every DOS boot sector.  DOS boot sectors are laid
out thus:
Jump to actual code start
'IBM 3.3', 00 - 8-byte system name
BIOS Parameter Block - between 32 and 50 bytes AFAIK.
Actual boot code.

The BPB contains information DOS needs about the disk - bytes/sector,
sectors/cluster, reserved sector count, FAT count, number of entries in the
root directory, number of sectors, the media descriptor byte, length of
tracks and FAT, number of heads, and in V4 upwards, the volume label and
serial number, plus an officially reserved system ID.  DR-DOS FDISK
incorrectly calculates some of these values, plus it writes a DR OEM ID in
the system name field.  Although this officially is correct, some IBM issues
of DOS look for the letters IBM in the system name, and report 'Invalid
media' otherwise.  Also, before DOS v3, the loader used the BIOS's BPB
rather than the one on the disk, so some DOS v2 issues didn't fill in the
BPB - these diskettes are unreadable on DOS 3 and up.

> The first MS fiasco that I ran across about this was when
> people tried to upgrade from MS DOS 3.x to MSDOS 5.0.
> What happened is that people that had MSDOS 3.x installed could
> not re-partition their drives with MSDOS 5.0 FDISK.
Probably because DOS 3 didn't know about anything > 32Mb, whereas DOS 4 and
up use a different partition ID to signify 'DOS Huge' (greater than 32Mb
partition).  MS-DOS 5's FDISK may have forgotten about that.

> Also, Does anyone know what variation of MSDOS is used with the NT Command
> Prompt? All I show when I run ver is WINNT 4.0.
It's called NT-DOS, as far as NT will tell me, and there's no 16-bit code in
there - so it's not a DOS variant, just an 'emulator'.

Regards,
Ben A L Jemmett.
(http://web.ukonline.co.uk/ben.jemmett/, http://www.deltasoft.com/)