On Fri, Dec 12, 2025 at 9:50 PM devin davison via cctalk <[email protected]> wrote: > It's been a while since i last wrote to the list. I have been reading up a > lot on early cnc systems. > > While recently picking up some left over tech from a shutdown machine shop, > spotted a early cnc system with some kind of minicomputer attached. Looked > to have some kind of tape drive and paper tape punch. It looked like it was > stored under a leaky roof, ball of rust, it looked too far gone to salvage > anything useful.
About 15 years ago, we had a Bridgeport Series II CNC mill with an original DEC LSI-11 processor board stuffed into a slot in all-Bridgeport hardware. In addition to manual operation on control switches, it had a Remax paper tape reader and a serial port to slurp up G-code. Because the PDP-11 only had 16K of RAM, you had to either run jobs from paper tape (which nobody wanted to punch in this century) or dribble the G-code in a manner described as "drip feeding". Given that a lot of modern designs coming out of your CAM engine are upwards of a megabyte, that's a lot of dripping. In the end, it was more trouble than non-technical folks wanted to deal with so it was scrapped for the price of scrap steel. I was allowed to strip whatever I wanted - I kept the PDP-11 CPU and the Remex reader. I have no idea specifically what programs were used in the 1970s to generate the G-code (though G-code can and was written up by hand). -ethan
