I built this sturdy and versatile microcomputer around 1982-85. Then we got our first child, my career took another path, time went by, PC’s came around (!), and I lost my interest in this nice piece of hardware. The other day I found all the parts, plugged them together, turned it on….. and it worked! (Please note the engraved and colored CRT control signs I made on the keyboard :-))
I even found all my old documentation, and if you are interested in these old 6502 processors, and especially in FORTH, you can see and download it all here.
These are my handwritten notes and drawings describing FORTH both in general and specifically for the 6502:
This is my hardware documentation:
My idea back then, was to create a workbench for I/O-modules and other interfaces, both analog and digital. I worked a lot with the very expensive CAMAC (google it) interface modules at Danfysik, but I wanted to make my own “cheap” modular interface system, that could do automated measurements and control, with plenty of built-in power supply, and of cause with a built-in microprocessor. The problem was to find the right processor and programming environment. My first attempt was to use the Signetics 2650 (that I knew well), and program it in assembler, but then I learned about the FORTH language on a couple of business trips to University of California in Irvine. I saw how incredibly fast you could implement ideas, and how fast it executed afterwards. Much, much faster than anything else at that time. I had been using the “Rockwell AIM 65” single board microcomputer with “clumsy BASIC” for another project, but suddenly it was possible to get the 6502 with a FORTH kernel. I then went for a design with a heavily modified AIM 65 (the bigger green PCB) placed in the upper compartment of the crate, as you can see here:
All the extra PCB’s and wires are all sorts of logic and drivers for the bus-extension, extra I/O, extra RAM, power supplies, remote control, etc. In the picture you can see:
You can reset from the front panel to boot with either embedded FORTH or embedded BASIC:
Tiny LED’s show all data and address bits on the front panel, just like on the mini-computers at that time.
Here is a close-up of the RAM-module. I just soldered a lot of DIL-chips sideways in two long rows:
If you look down into the crate, where the modules are supposed to go, you will see two fixed boards. The one to the left is the address/R-W-enable decoder for each slot, and the one to the right is a CRT-driver board (not made by me):
A close-up of the decoder board:
I remember that one of the last things I wanted to implement was a disk-drive. But as it is now, the only way of storing programs is on this “cute” cassette recorder, made especially for data:
It still works after all these years. Listen to, and see the CRT initialization program loading from the cassette:
As I mentioned earlier, I never really used this microcomputer, and I only built a few modules. One module to mention is this massive digital I/O module with LED indicators for every bit:
The I/O board:
And here one great thing to be used together with the I/O module, a universal ROM/EPROM burner, that was the last thing I did before I lost interest: