DECmate III and Rainbow 100+

From: Kevin Handy <>
Date: Tue Feb 22 11:02:35 2005

Vintage Computer Festival wrote:

>I'm trying to get either of these systems running in the hopes that I can
>access what I believe to me a 5.25" disk with an RT-11 filesystem on it.
>Both systems have a video port and a COMM port. I tried connecting a
>VT510 to the COMM port on each system but didn't get anything (at either
>9600 or 19,200 bps). I can't find my VR201 to check if video is coming
>out either one.
>Both systems access drive 0 of the RX50 upon boot-up. The Rainbow 100+
>has an internal hard drive but I don't hear it booting from the drive.
>Anyone have any experience with these guys?
Both require the monitor/keyboard to see the boot-up. They don't boot
on the serial port.

Neither is a PDP-11, nor do they run anything that will natively read
RT-11 file systems.

The Rainbow is a 8086 with a Z80 coprocessor (it's not PC compatable),
and will boot into either MS-DOS or CPM-86. CPM-86 cost about 10X
what MS-DOS did, so wasn't used much.

The Decmate-III is a PDP-8 compatible, probably used for running WPS-8,
and may have a 8086 and/or Z80 coprocessor for CPM or MS-DOS.


For reading raw RX50 images, I've had the best luck using a linux box
with a 1.2Mb floppy disk, and either using the 'dmklib' toolkit with
its floppy reading program, or an entry in the /etc/fdprm file and
using a command like "cat /dev/fd0 > raw.dsk".

If you use dmklib (preferred over the fdprm option), you may have to
play with the command line options to get it working correctly
(force single sided at minimum).
I have also used it to read Kaypro-II floppies.
It is available at:

For the fdprm setting. Try ONE of the two following lines. I usually find
the second to usually work best on my hardware, but sometimes the
first works better. comment out the line you do not use (# in front of

rx50 800 10 1 80 0 0x25 0x01 0xDF 0x2E
rx50 800 10 1 80 0 0x14 0x01 0xDF 0x18

Note, that Linux doesn't handle disks that start numbering the sectors
with 0, but the dmklib routine does.


Once you have the raw images, you should be able to locate various
programs to examine them, or just mount them in a pdp-11 emulator
like 'simh'.
Received on Tue Feb 22 2005 - 11:02:35 GMT

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