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This mini forum is intended to provide a simple means of discussion about the Digital Equipment Corporation RAINBOW 100 computer. If you want to share your own experience or memories, or add relevant information about this system: post a message! For other purposes like sales messages, hardware & software questions or information requests, please use our main forum.

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Sunday 15th May 2016
Manny (Usa)

I Have rainbow software i see people are looking for

Sunday 16th December 2012
Brian Richards (USA)

Suitable Solutions sold not only the 286 accelerator boards and clock chips but also DOS3.10 AND the adaptation kits for Windows/286 and later Windows 3.0. You could run MS-Excel (which was a poorer number-cruncher than 1-2-3 but did offer better publication graphing). Suitable Solutions also sold the I-Drive- external DS/DD IBM format drive. $I''m reminded of this as I inventory my Rainbow equipment for eventual ebay-ing or other sale)

Saturday 18th December 2010
Mark Graybill (United States)
Intersecting Concepts

I have a fondness for the Rainbow 100 because it was how I started my software business back in 1983 (after selling a beautiful ''67 SS 350 Camaro to buy the Rainbow. I still have the very first DEC Rainbow sold by Computerland in the San Fernando Valley.

I originally wrote a formatting program for the Rainbow, and later wrote Media Master, a disk-to-disk format conversion program. That work in the floppy disk controller world eventually led to the creation of the Fastback Plus backup programs for the Mac and PC.

Dan Pleasant brought Code Blue to me to market while he was working at HP back in the day. He later was a major contributor to Fastback for the Mac. If you guys are interested, there is some history posted at the homepage URL.

For those trying to figure out direct screen I/O, I would say it is extremely difficult. I poked around the BIOS back then to try to help my friend Dave Grenewetski (later the CEO of Mindscape) figure out how he might port his graphics program on the Osborne to the Rainbow. I don''t remember the exact reason why now, but I do know I concluded it was more work than the market size merited.

Saturday 9th October 2010
Douglas W. Goodall (United States)
Douglas Goodall

I recently restored a Rainbow 100 and I am trying to write some software for it. It is slow going with only the BDOS calls. I wish I could talk to the hardware a bit. Any information would be very appreciated I was a Digital Research Engineer and have a fondness for the machine.

Friday 2nd April 2010
Fred Einstein (Cincinnati, OH USA)

While working at DEC, I actually wrote MS-DOS 3.3 for the Rainbow 100. The machine had several operating system choices for it. You could run CPM-80 on the Z80 microprocessor, CPM/86 on the 8088, MS-DOS on the 8088, VENIX (a UNIX v5 implementation) on the 8088, MPM (a multi-tasking version of CPM/86), and even Windows 1.0 which was adapted for the Rainbow at DEC by a guy named Alpo Kalio (a brilliant engineer). Windows ran on the hardware-assisted graphics card. The unique part of the hardware is that the two CPU''s could share a 2K space in RAM which allowed them to communicate. Thus, the floppy disc handling was done totally by the Z80 while the rest of the system I/O was done by the 8088. Pretty advanced engineering!

The biggest definciency of the Rainbow was the fact that early versions of it had no support for software writers. On the IBM PC, you could call various BIOS functions such as INT 10H to do elementary text and graphics on the screen. The Rainbow, until DOS v2.11 had no such support. Thus, software writers such as Lotus 1-2-3 had a heckava time trying to talk directly at the hardware in order to do text and graphics. Later on, as the Rainbow was dying, I produced a complete Software Development Kit for the Rainbow which had a rich set of interfaces for doing text and graphics. I also wrote a driver so that the Rainbow could read and write single-sided IBM floppies and so that the IBM PC could read Rainbow''s 10 sector per track single sided floppies.

Later on, the morons at DEC (which had a very hierarchical management structure) tried to clone the IBM AT in a single box. They called this monstrosity the VAXMate. Unfortunately, one of the engineers who was working on the non-infringing BIOS actually stole some of IBM''s code verbatim. This caused all sorts of legal problems for DEC. Ken Olsen, the short-sighted owner of DEC, demanded that the VAXMate be produced with monochrome EGA graphics and without a fan. Thus, the thing constantly overheated. I think that DEC may have sold 1 or 2 of these horrid machines. I had already departed for Microsoft by the time that DEC tried to get this VAXMate thing off the ground.

Sunday 17th May 2009
Rich Allen (Tucson AZ USA)

The Rainbow 100 was the computer I really wanted but couldn''t afford. It could run CP/M and MS DOS... in those days there was a trove of CP/M software and DOS was just getting off the launch pad. I miss the days when there were so many different platforms.

Thursday 15th June 2006
S.R. (USA)

I used to use Code Blue, an IBM PC Emulator, to run Omega. A very enjoyable Rogue-like game. The dungeons took upwards of 15 minutes to load.

Also there was an excellent word processor, WPS for both CPM and DOS.

Friday 1st April 2005
Mike T. (UK)

The text mentions that the DEC introduced a 80286 based system called a VAX-station - this was I expect actually a VAX-mate (or DEC-mate). (A VAX station is a different thing altogether).

It also appears to be little known that the DEC Rainbow had hi-res colour graphics and that it was possible to display graphics and text on two separate screens at the same time (one text only and the other for colour graphics) - not bad for a machine that came out before the PC era even started...

It's biggest technical flaw was the lack 'standard' interface bus - in the end this didn't matter as DEC simply didn't comprehend the potential for a market in personal computers.

Sunday 2nd November 2003
J.C. (United States)

I found some old "Rainbow 100" floppies in a garage sale. I plugged in my ol' 5.25" drive into a fairly modern system with Linux installed. It turns out that if you tweak the /dev/fd0 device using setfdprm it's possible to copy off the contents of the Rainbow 100 floppies. Just specify that the disk is single-sided, double-density, 10 sectors/track, 80 tracks, 800 sectors total, 512 bytes/sector. The sectors are organized by a 2:1 interleave pattern except in tracks 0 and 1 (I don't know how to tell setfdprm this). Don't forget to try adding rate=1 when using setfdprm. You should be able then to use dd or cp to copy the contents to a file. Even when this is done, however, don't expect to be able to mount it. The first two tracks are loader code, or something. One floppy had MS-DOS 3.0 on it and I couldn't find the boot sector (but the FAT and root directory began immediately on track 2) so extracting files would probably involve manually copying parts of the image to other files.

Good luck.

Monday 2nd June 2003
Frank Gilbert (Earth)

Thanks for the great site. Nostalgia for us old-timers. I remember porting a BASIC program I had written for the PC, to the Rainbow. All the screens had to be re-coded as Rainbow only had 23 lines while the PC had 24. Bummer!

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