I think Coherent, of Mark Williams, is a bit older. According to Wikipedia it was first released in 1980, but probably was for the PDP-11, at that point. I use

I think Coherent, of Mark Williams, is a bit older. According to Wikipedia it was first released in 1980, but probably was for the PDP-11, at that point. I used it on an 80286 for years. https://en.wikipedia.org/wiki/Coherent_%28operating_system%29?wprov=sfla1 https://en.wikipedia.org/wiki/Coherent_%28operating_system%2...