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Digital Rainbow (PC100-B2)


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  Digital Rainbow (PC100-B2) by Bill Degnan - 04/20/2017 23:55
DEC Rainbow PC100-B2 with VR241
This is the Rainbow PC100-B2 I restored from three systems' parts. I used the VR241 display from the previous dead Rainbow PC100-B2's I had been working on and now I finally have a system that works. Click image for larger view.

DEC Rainbow base model with VR201
This will not do....these VR201's are hard to find without screen rot. Click image for larger view.

I got this message from I Primus who suggested ways to deal with the VR201:

"..The cable to the VR201 is very, very simple. It contains monochrome
composite video, and the direct passthrough for the keyboard lines.

You can make up an adapter to allow you to use a standard monochrome
composite monitor and the LK201 keyboard.

Pin 12 - monochrome composite video signal
Pin 4 - video shield ground

Pin 5 and 6 - ground
Pin 7 and 8 - 12V
Pin 14 - RX data keyboard
Pin 15 - TX data keyboard

See here for the pinout of the LK201 keyboard:

You can rig up this adapter and use any normal monochrome composite
monitor with the Rainbow. Best results on quality monitors with
adjustments for height, it'll overscan on some things like security
monitors. Likewise, it's real easy to rig up the VR201 to work on
anything else, it's a fantastic, sharp, clear little monitor. The
screen rot can be fixed, I've done a few CRTs like this. You basically
need to remove the tube, heat the faceplate very carefully with a heat
gun to get it to delaminate, clean all the gunk out, and stick it back

More pics

  Color Graphics by Bill Degnan - 04/22/2017 19:06
DEC Rainbow Pacman clone. Note the colors. Click image for larger view.

The part number is 5015687. Just as with the other adapters they're installed onto the motherboard, there are no expansion slots.

DEC Rainbow SoftWright Systems' ChessWright program (in demo mode). As good or better than the IBM PC EGA display in my opinion. Click image for larger view.

  LCTERM by Bill Degnan - 04/22/2017 23:53
DEC Rainbow PC100-B2 running LCTERM to connect to C.H.I.P. computer
I used the program LCTERM to connect from the Rainbow communications port to my C.H.I.P. computer. Click image for larger view.

DEC Rainbow PC100-B2 connected to CHIP running simH
The Rainbow COMM port defaults to 7N1, my CHIP wants 8N1. The LCTERM program is pretty primitive and does not offer a switch to change the stop bits value within the program itself, instead relying on whatever the operating system has set. So I chose MS DOS v 3.10b for Rainbow sold by Suitable Solutions because it comes with a command called SETPORT that one can use to change the Rainbow's COMM port data bits from 7N1 (default) to 8N1 (what the CHIP expects). Pictured is a photo of the system after exiting simH and then running a directory command (ls). Click image for larger view.

  8087 / Memory Adapter by Bill Degnan - 04/22/2017 23:57
InfoCom Starcross for Rainbow Disk
Pictured is the InfoCom Starcross for Rainbow Disk in CP/M format. InfoCom issued versions of its popular text adventures for Rainbow CP/M not MS DOS as far as I can tell. Click image for larger view.

Rainbow Memory Extension card
Running Starcross caused a not enough memory error. Hmmm, better check the RAM card. Pictured here is the partially-populated memory extension card I found installed in the system. Ah-ha...I assumed seeing the empty slots that I can fix the memory issue by adding more 21414 RAM chips. Click image for larger view.

When I went to look for some 21-21414-01 RAM chips I found a 8087 co-processor and RAM expansion card to use instead. The 8087 will come in handy when I attempt to install and use VENIX. The 8087 memory adapter card will upgade a Rainbow up to almost 900K usable RAM. Click image for larger view.

To install, first I removed the i8088 CPU chip from the motherboard located under the hard drive controller. Click image for larger view.

Next I installed the 8087 card into the space formerly occupied by the Memory Extension card. I also attached the expansion card cable into the 8088 slot. The 8088 I removed earlier was transplanted into the Memory Adapter. Click image for larger view.

First reboot after making any RAM change triggers the system to report that the system change was detected. Message 24". Click image for larger view.

Starcross still reports that there is not enough RAM! I double checked that the RAM is present and available, not sure yet what is causing this to happen. I am still glad I upgraded the RAM but bummer Starcross is not happy.

  VENIX Installation by Bill Degnan - 04/23/2017 06:04
My interest in the Rainbow gained new life when I was contacted by Warner L. about the original VENIX distribution disks I reported getting from the U of Delaware here, which apparently are very hard to track down. VENIX is the UNIX derivative for DEC Rainbow created by Tarik Isani. At the time Warner originally contacted I had no working Rainbow to use to copy the disks nor did I have a quad-density drive in my disk imaging system to copy them. So, I sent him the disks so he could image them, and I also scanned the installation instructions from the manual. Yes I need to copy the entire thing at some point, 6 binders.

About the same time I picked up a third Rainbow system that I could use for parts. This one had a working motherboard but no monitor. It was finally time for me to put the three systems together into one running Rainbow. What you read above is all of the results.

Warner got VENIX up and running on his Rainbow. Good, the disks work. I found another copy of the disks (minus the 1st/XFER disk) so I did not have to use the originals.

More about VENIX:

In anticipation of receiving the returned disks I partitioned the hard drive to hold VENIX plus a small MS DOS partition for utility purposes. Stand by...Warner suggest I use the files he uploaded to his site, or at least get his copy of the XFER disk by using rbimg (iwrite) utility. Not sure yet how that works.



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