Message-ID: <010901c09d3d$0a4a9600$a208e289@mpaul>
From: "Matthias Paul" <Matthias DOT Paul AT post DOT rwth-aachen DOT de>
To: <opendos AT delorie DOT com>
Cc: <fd-dev AT topica DOT com>
References: <20010216 DOT 032625 DOT -270235 DOT 0 DOT domanspc AT juno DOT com>
Subject: Re: Max. drive letter, etc.
Date: Fri, 23 Feb 2001 02:45:06 +0100
Organization: Rechenzentrum RWTH Aachen
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Reply-To: opendos AT delorie DOT com

On 2001-02-16, Robert W Moss wrote:

> When DOS boots it automatically assigns C: to the first 
> primary  partition on the first hard disk and then assigns 
> D:, E:, etc.. to all the primary partitions it finds and then 
> assigns the remaining Alpha ID's to the logical partions 
> on all extended partitions.  After that it assigns all the 
> removable drives and CD ROM drives.  
> [...]
> So what happens when it hits 24?  ANYONE??

MS-DOS 6.xx displays an error message similar to "Too many
block devices. Drives past Z ignored" for any drives past Z:,
DR-DOS just skips these drives silently. 

However, under Novell DOS 7 and above you can 
use LASTDRIVE=27..32 to expand the CDS table.
The corresponding drive "letters" are [: \: ]: ^: _: and `:
(hope this comes through in the mail). It may be difficult
to impossible to use these drive letters in applications
as most tools are only designed to handle 26 logical drives.
(f.e. 4DOS does not allow to access the drive `:).

According to "Undocumented DOS", the idea to use
drives past Z: was originally born by Novell NetWare
for its so called "search drives" (at least for the IPX/NETX
drives, this works even without LASTDRIVE=32 in
CONFIG.SYS). My research revealed, however, that
even DR DOS 3.41 and 5.0 *internally* supported 32
drives during CONFIG.SYS (but no LASTDRIVE=32
directive), but they used a completely different scheme
to maintain drive related data and had no equivalence
of a CDS, anyway.

MS-DOS 7 adapted this model and also supports
the LASTDRIVE[HIGH]=1..32 syntax in CONFIG.SYS,
and this variant was added to DR-DOS 7.02 as well
(which also allows for [HI]LASTDRIVE[HIGH]=[..`).
Unfortunately, some kernel bugs in MS-DOS 7.10 may
cause the system to collapse for drives past Z: with some
API functions.

 Matthias

PS. This gets CC: to the FreeDOS mailing list, since the
original thread in the OpenDOS list was cross-posted
to both lists.

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Matthias Paul, Ubierstrasse 28, D-50321 Bruehl, Germany
<Matthias DOT Paul AT post DOT rwth-aachen DOT de> <mpaul AT drdos DOT org>
http://www.rhrz.uni-bonn.de/~uzs180/mpdokeng.html
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