FORTH/BASIC Microcomputer, 1985


I built this sturdy and versatile microcomputer around 1982-85. Then I got married, 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.¬†Recently I found all the parts, plugged them together, turned it on….. and it worked! Even the builtin thermo-printer was still working with 30 years old paper ūüôā

I also found all my old documentation, and if you are interested in the old 6502 processors, and especially in FORTH, you can see and download it all here:

FORTH notes by cTOPc


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 interface modules at Danfysik, but I wanted to make my own “cheap” modular interface system. It should be possible to 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 UCI in Irvine, CA. 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 a year later it was possible to get the 6502 with a built-in FORTH kernel. I then went for a design with a heavily modified AIM 65 placed in the upper compartment of the crate, as you can see below. On the front panel tiny LED’s would show all data and address bits, just like on the mini-computers at that time. The extra PCB’s and wires are all sorts of logic and drivers for extra¬†memory, serial I/O and¬†bus-extension for the crate bus:


From the front panel you can reset and boot with either embedded FORTH or embedded BASIC:


The first things I made for the system was a massive universal parallel output module, and a universal PROM burner for that module:


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 a special cassette recorder. It still works after all these years. See and hear the CRT initialization program loading from the cassette:


The AIM65 schematics are here:

AIM65_1    AIM65_2    AIM65_3