A nice video by YouTuber Usagi Electric, booting his newly acquired Rainbow 100 in CPM/80 mode, 8088 powered MS DOS (with smooth scrolling!), and in VT-100 mode. (The Rainbow 100 has yet another trick up its sleeve, namely CPM/86, and a few third party operating systems, like USCD-p and Concurrent CPM, as well.) But, before this, we get a look at the internals, a pretty enjoyable experience for the design and built quality of these DEC machines.
However, the Rainbow 100 has also a few idiosyncrasies, which ultimately limited its amazing range of compatibility.
(The machine seen beside the Rainbow is a PDP-11/83, running RSTS/E.)
When I first heard about the DEC Rainbow, way back in the day, I was unimpressed because I only saw an MS-DOS machine - and one that wasn’t very compatible either.
When I watched this video last week, I was surprised that it came with a VT-100 in ROM plus a Z-80 to run the old CP/M stuff. That CP/M-86 runs on it didn’t surprise me. I have an old 8088 system with CP/M-86 running to play with.
But these hybrid systems seemed like to have a very limited market. Like the Commodore 128 (which also had a Z-80 and could run CP/M), the Rainbow seems to have been a box of compromises to try to be everything to everyone - and failing to be anything to all but a few.
DEC’s PC strategy was somewhat complex and mostly based on their successful PDP lineup (but, like the Rainbow, these had some crucial compatibility issues): there was PDP-8 based DECmate II, and the Professional line (Pro 325, Pro 350, eventually the Pro 360) based on a PDP-11 on-a-chip. Apparently, the Rainbow was meant to cover a (somewhat lesser) other systems/OS base. I’m not sure, how and to what extent this relates to DEC’s rather ill-fated strategic analysis, which saw them facing a Japanese challenge, while somewhat ignoring IBM (and clones of the IBM PC).
An obligatory video in this context is the following one on DEC’s quest for the PC:
(Also interesting to see after having watched the previous video showing the solid internal design of the Rainbow, is the unforced error regarding the cost-effective keyboard.)
I remember when the Rainbow came out. It was offered at a slight discount at my college. It had a bad reputation - as slow and expensive. Now I own one, so I can format 5.25" floppies for my DEC Pro. No joke.
