Message-ID:	<004a01c0cdf7$809a83c0$b508e289@mpaul>
From:	"Matthias Paul" <Matthias DOT Paul AT post DOT rwth-aachen DOT de>
To:	<opendos AT delorie DOT com>
References:	<Pine DOT LNX DOT 4 DOT 30 DOT 0104241245460 DOT 9349-100000 AT med-physio11 DOT bu DOT edu> <000201c0cd28$809358e0$aa08e289 AT mpaul> <3AE71D20 DOT 430AF36F AT cornell DOT edu>
Subject:	Re: USB in DOS
Date:	Thu, 26 Apr 2001 02:51:53 +0200
Organization:	Rechenzentrum RWTH Aachen
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Reply-To:	opendos AT delorie DOT com

On 2001-04-25, Alan S. wrote:

> But some people in the HARDWARE end of the business must still see
> possibilities for DOS [et al] USB - I just puchased a [1999 vintage?]
> PCCHIPS 598LMR motherboard, in which the AMI BIOS contains 2 options:
> 1. "USB function"           (with values "enabled" & "disabled")
> 2. "USB function for DOS"   (with values "enabled" & "disabled")

Iīm not familiar with the options found in recent AMI BIOSes, as most
machines have Award BIOSes over here, but I assume that these
options are not to *enable* an obsure USB function *for* DOS, but in
fact are they exist to allow DOS to be used *with* (at least some) USB
devices by emulating legacy devices via the traditional BIOS functions.
For example, many Award BIOSes have an option "USB legacy
keyboard", and if enabled, you can use an USB keyboard as if it
was a traditional serial keyboard attached to the DIN or PS/2
connectors. That is, it will generate an INT 09h when a key is
pressed or released, and the keyboard driver (KEYB) can still
access the traditional I/O ports (in the "keyboard controller" on
the mainboardīs chipset) to retrieve the make/breakcodes or to program
the LEDs etc. In theory, a similar feature might be available for
USB modems (to show up as a logical serial port) or USB
printers (to be logically accessed as a parallel port), but I have
yet to see such kind of emulation. Anyway, all this masquarading
takes place at the ROM-BIOS level, so that from DOSī view, there
would be no difference compared to a traditionally equipped system.

Without such kind of legacy support, you would have to load
USB protocol stacks (similar to a network driver stack)
and even then would probably still have problems to use
USB devices from within existing DOS applications.

I know of at least one (commercial) USB stack implementation
for DOS, "USB4DOS", but I didnīt tried it so far. Anyone?
But since the USB protocol is quite complicated, I assume
a full implementation consumes much memory...

 Matthias

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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>
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