ROM2DISK / DISK2ROM 1.00                        John Elliott, 10 November 2017
==============================================================================

  The Toshiba T1000 laptop has an unusual feature: a 256k ROM drive 
containing a copy of MS-DOS 2.11, allowing the machine to be booted 
without the use of a floppy disc (there is no hard drive).

  ROM2DISK and DISK2ROM convert between the file format used by the Toshiba
ROM image, and a standard disc image (or an actual 3.5" floppy drive). This 
allows replacement boot ROMs to be constructed -- though as the programs are
currently constituted, it isn't possible to make a bootable ROM image that
contains a different version of DOS.

  To use:

  ROM2DISK { options } file.rom file.vfd 

  Converts the ROM drive to a floppy image file that can be used in an 
emulator / virtualisation solution. Options are:

  -type <t>: Disc image output format. This is normally a raw 'drive image' 
        file, but '-type floppy' specifies that a floppy disc will be 
        written. In this case the output filename should be the name of 
        the drive.

  -comp <c>: Compress the output file with the specified compression 
        algorithm. Unlikely to be useful.

 
   
  DISK2ROM { options } file.vfd file.rom

  Converts the specified floppy image file to a ROM image that can be used 
in an emulator or burned to an EPROM for use in genuine hardware. Options 
are:

  -type <t>: Disc image intput format. This is normally a raw 'drive image' 
        file, but '-type floppy' specifies that a floppy disc will be 
        read. In this case the output filename should be the name of 
        the drive.

  -comp <c>: Compression algorithm used on the input file. Unlikely to be
        useful, as it should be detected automatically.

  -128: Create a 128k ROM image.
  -256: Create a 256k ROM image.
  -512: Create a 512k ROM image (default).

Some notes on creating an alternative ROM image
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* The process is designed for 720k disc images. Other disc formats may
 work, but they must have 9 sectors per track, because this value is 
 hardcoded in the T1000's BIOS.

* Whatever size of ROM is generated, it's smaller than 720k. DISK2ROM will
 warn about files that fall outside the area of the ROM. On the original 
 ROM, there's a hidden file called DUM that occupies this space.

* Currently, only ROM images made with the T1000's original MS-DOS 2.11 
 will boot. This is because the ROM drive appears to MS-DOS as a hard 
 drive with no partition table; most versions of DOS can't cope with this,
 and so will fail to find their own system files.

  The way to fix this would be to generate a Master Boot Record and partition 
table at the start of the ROM image. That's rather beyond the abilities of 
the current DISK2ROM -- not to mention that the resulting file would not be 
readable by ROM2DISK.

