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+

+       Rainbow Disk Image Utilities

+       ============================

+

+       The files contained in this archive are utilities for creating disk

+   images from RX50s and regenerating disks from said images.  The

+   utilities are meant to work with MS-DOS version 2.11 or later on an

+   actual Rainbow 100 personal computer only.

+

+       The programs utilize RAW disk image format, which is a byte-by-byte

+   dump of all data on the disk in increasing track and sector order.  The

+   RX50 disk drive (at least as implemented on the Rainbow 100) is an

+   80-track drive with 10 sectors/track and 512 bytes/sector.  The RAW

+   image format for a Rainbow would be as follows:

+

+       Beginning of file: Track 0 Sector 1

+                          Track 0 Sector 2

+                          ...

+                          Track 0 Sector 10

+                          Track 1 Sector 0

+                          ...

+       End of file:       Track 79 Sector 10

+

+       With each sector containing 512 bytes, a valid RX50 image should be

+   exactly 409,600 bytes long.  If the image file is a different size when

+   recreating a floppy disk, results are unpredictable.

+

+       These utilities make use of Rainbow interrup 0x65 for all

+   reading/writing.  A true Rainbow RX50 floppy has sector skewing

+   implemented in both MSDOS and CP/M, meaning that physical sectors do not

+   equal logical sectors.  Logical sectors are the way the operating

+   system(s) access the floppies, whereas the physical sectors represent

+   the actual layout on the disk.  The call to interrupt 0x65 assumes the

+   calling program wishes to access everything by logical sector.  The RAW

+   image format, however, would actually use physical sectors.  The

+   utilities automagically "unskew" the sectors when creating an image and

+   "reskew" the sectors when writing the disk.

+

+       Logically addressed images can be dealt with as well by using the /L

+   option with the utilities.  This option enables logical addressing.  The

+   benefit of a logically addressed image file is that it may (but not for

+   sure...) be able to be mounted under operating systems that allow

+   mounting image files (i.e. GNU/Linux or *BSD).

+

+       A summary of the utilities appears below:

+

+       iwrite.exe

+       ==========

+

+       The iwrite utility is used for regenerating a floppy disk from an

+   image file.  The syntax is:

+

+       iwrite F:\path\to\image.img Drive

+

+       The Drive should be a single letter specifying an RX50 drive to

+   write to (A, B, C, or D, where applicable).  Formatting the floppies

+   prior to writing should not be necessary.  For example, to write the

+   image file "dos310b.img" to the B: drive, the following command would be

+   used:

+

+       iwrite dos310b.img B

+

+       The /L option can be used if the image file is known to be logically

+   addressed.

+

+       icreate.exe

+       =========

+

+       The icreate utility will create a new image file by reading the

+   contents of a true RX50 diskette.  The syntax is identical to the iwrite

+   utility:

+

+       icreate F:\path\to\image.img Drive

+

+       The Drive parameter is a single letter specifying the drive

+   containing the disk to image (A, B, C, or D, where applicable).  The

+   drive must be a true RX50 drive.  For example, to image a disk in the A:

+   drive and store the result in the file "cpmv20.img", the following

+   command line would be used:

+

+       icreate cpmv20.img A

+

+       The /L option can be used to generate a logically addressed image if

+   desired.

+

+       Skewing

+       =======

+

+       As stated ealier, the Rainbow employs a skewing scheme on RX50

+   diskettes.  Tracks 0 and 1 are not skewed (logical sector == physical

+   sector), whereas all other tracks use the following skew table:

+

+       Physical    Logical

+       1           1

+       2           6

+       3           2

+       4           7

+       5           3

+       6           8

+       7           4

+       8           9

+       9           5

+       10          10

+

+       I do not personally know the reasons for the above, but the table

+   works.  The table was lifted from the source code of ImpDrive by M.

+   Warner Losh.

+

+       Compatibility

+       =============

+

+       These utilities use a true RAW image format.  The iwrite utility has

+   been tested with and is completely compatible with Will Kranz's

+   wteledisk utility.  Wteledisk can convert Teledisk *.td0 images into RAW

+   image files.  The resulting RAW image file can then be written to an

+   RX50 using the iwrite utility.  The /L option should not be used in

+   these cases.

+

+       Building

+       ========

+

+       The utilities were compiled using Borland Turbo C 2.0 on an actual

+   Rainbow 100.  The executables can be generating by running:

+

+       make all

+

+       The code does not use any Borland extensions, but does rely on the

+   int86() and segread() functions from dos.h.  It should be possible to

+   compile this code with Microsoft C as well, although the make file

+   certainly will not work.

+

+       Support

+       =======

+

+       Anyone needing support with this utility or encountering bugs with

+   various images can contact me at jeff@rainbow-100.com.  These utilities,

+   although at version 0.1, are completely capable.

+

+       Copyright

+       =========

+

+       The utilities and their source code are copyrighted by Jeff

+   Armstrong and released under the GNU General Public License version 3.

+

+       The real meat of the licensing:

+

+       Rainbow Image Utilities

+       Copyright © 2008 Jeffrey Armstrong <jeff@rainbow-100.com>

+       http://jeff.rainbow-100.com/

+

+       This program is free software: you can redistribute it and/or modify

+       it under the terms of the GNU General Public License as published by

+       the Free Software Foundation, either version 3 of the License, or

+       (at your option) any later version.

+       

+       This program is distributed in the hope that it will be useful

+       but WITHOUT ANY WARRANTY; without even the implied warranty of

+       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+       GNU General Public License for more details.

+       

+       You should have received a copy of the GNU General Public License

+       along with this program.  If not, see <http://www.gnu.org/licenses/>.

+       

+       The full license is compressed in COPYING.ZIP.

+

+       ---

+       Jeff Armstrong

+       http://jeff.rainbow-100.com/

+       jeff@rainbow-100.com

+

+       January 15, 2009