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Message-ID:	<000c01c1acfb$c4836a00$c03dfea9@atlantis>
From:	"Matthias Paul" <Matthias DOT Paul AT post DOT rwth-aachen DOT de>
To:	<opendos AT delorie DOT com>
References:	<200202020502 DOT LAA00990 AT ftp DOT lanka DOT net>
Subject:	Re: USB, FAT16 in DR-DOS, scanner software for DOS
Date:	Sun, 3 Feb 2002 22:43:04 +0100
Organization:	University of Technology, RWTH Aachen, Germany
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On 2002-02-02, Michael Snowden wrote:

> o I would like to learn if there are scanners available for use with
>   DOS. I am using Windows DOS 7.0 on a Compaq Armada laptop and an
>   IBM Net Vista desk top. I am not using the Windows system, only the
>   operating system that comes with it: DOS 7.0.
> 
>   I have seen a very attractive scanner by Canon called the Cano Scan
>   N640Pex, which comes for either a parallel or USB port. I doubt
>   seriously that Canon or any other compamy makes DOS software for
>   scanners, but I would like to know if someone else has made them. 

Well everything is possible in theory - and in software. There are
several active projects to make USB devices accessable under DOS,
and there may be drivers for special devices like keyboards or mice,
but I doubt there will ever be a general solution that will work for
all USB devices no matter what they do. USB is a quite complicated
architecture, and it requires much memory to implement the software
side. So, it is nothing for real mode DOS if it should still be
useable for desktop applications afterwards, it would at least
require that the drivers use DPMS or CLOAKING to run in Protected Mode.
What I have heard of so far have been (often proprietary) libraries
to link into dedicated applications so that they can access some
special USB devices, but this is not what I would call a general
purpose solution which would add some form of standard interface
to the OS, where the USB devices become accessible in an easily
to use form, like, for example, PCMCIA/PC Cards and similar "devices"
can be used in a mostly transparent fashion by DOS applications.

> o Should I seek a parallel or USB port for a scanner?

Parallel.

My general advice for people who do not want to live in
a Windows-centric and -dependant world is to:

- Never buy GDI-, WPS-, or WinPrinters. These kind of printers
  cannot be used under DOS. Being "compatible with Windows
  Printing System" is not a checklist item (not because we
  /use/ DOS, but just because being optimized for Windows
  is almost equivalent with a very cheap and limited design
  for the ultra-low market segment), whereas being compatible
  with DOS or Linux is a sign of quality, careful design and
  technical superiority, because these printers can be used
  under Windows as well (even if Windows would not be listed
  on the box).
  The more expensive PostScript, PCL or ESC/P printers can be
  used under DOS and other systems, provided that you find a
  driver, or your software allows to configure the control
  sequences. They usually also have other goodies, so I generally
  donīt suggest to buy low-cost hardware. WinPrinters have no
  "intelligence" on there own and they will never work in and
  under DOS, few of them can be used with Linux meanwhile.
  
- Avoid USB or FireWire devices, use classical PS/2 or serial
  mice, PS/2- or DIN-keyboards, parallel port printers and
  scanners. Use SCSI for mass storage or external data devices
  that might need higher transfer speeds than a parallel port
  can provide, like ZIP drives, streamers, scanners, removable
  disks... Or for high speed far distance connections use
  Ethernet networking.

- Never buy SoftModems or WinModems, or any "sound card" that
  can plug into your AMR slot on the mainboard. An indicator
  that a modem can be used in *any* operating system, past,
  present, and long foreseeable future, is that it is an
  *external* device and that it uses a RS232C serial connection.
  
  For high speed modems beyond V90/V92 and ISDN use Ethernet
  again.

> o I would like to know the limitations of the DR-DOS  FAT16 system
>   and whether or not it will support hard drives bigger than 2
>   gigabytes for a given partition.

The limit for FAT16B is 2 Gb, this is not a limitation of DR-DOS,
but of FAT16, which means there can be only approx. 65535 allocation
units ("clusters") on the partition, and the maximum size for each
of them is 32 Kb in any DOS (64 Kb in Windows NT and FreeDOS only).
The only way to have larger partitions is using FAT32, but this
has other shortcomings, some of them being compatibility of
the disk tools and the kernel, significantly reduced speed
without excessive caching which is not possible under DOS, and
memory occupation for the driver.
The maximum drive size DR-DOS and any other classical DOS, including
MS-DOS 7.0, is 8 Gb per physical disk. This limit is imposed by the
CHS (Cylinder/Heads/Sectors) interface DOS uses to access disks.
It is possible to use larger physical disks, but DOS sees only the
first 8 Gb of the drive. There is no remedy for MS-DOS 6.22 or
PC DOS 2000, but you can use a trick under DR DOS 6.0+ to at
least use 8 Gb (instead of the usual 2 Gb) under DR-DOS without
sacrifying system stability, reliability, or comfort, and still
let other OS see the whole drive.
If you want to use 8 Gb for DOS, but still want to use the
remainder of the disk for other OS, create primary partitions
and logical drives in an type 05h extended partition to occupy
all the space up to 8 Gb under DR-DOS 7.0x, then patch the
partition type from 05h to C5h, and then reboot under MS-DOS 7.10
and create an extended partition type 0Fh with any kind of logical
drives in there above the first 8 Gb. Afterwards you can use up to
8 Gb disk space under DR-DOS per physical disk, and all the remainder
above can be used under MS-DOS 7.10 or other OS which support LBA.
Only the primary partitions C: will be usable and seen by both OS.
This will also have the advantage that Windows 9x does not pollute
the DR-DOS FAT partitions with its long filesnames...

Greetings,

 Matthias

-- 
<mailto:Matthias DOT Paul AT post DOT rwth-aachen DOT de>; <mailto:mpaul AT drdos DOT org>
http://www.uni-bonn.de/~uzs180/mpdokeng.html; http://mpaul.drdos.org

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