Most likely this system was running UniFLEX. Uniflex was a small, very Unix-like OS that did feel a lot like Unix, maybe V5 or V6. As I recall the kernel was about 16K and written in assembly language. I only know this because at one point I disassembled it and clearly some parts of it were not generated by a compiler. Not to go into great detail, but one example was a function that looked at the return address to find out where it was called from to act differently depending on the caller.
Many of these systems handled memory above the 6809's 64K address space by feeding the top four address lines into the address lines of a 16x8bit RAM chip creating an address space of 256 4K pages (up to !MB!) that could be mapped into an individual process's address space. It was a cleaver little hack.
I just found this link: https://en.wikipedia.org/wiki/... It's funny because in mentions the Introl C compiler, which I happen to have written.
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Many of these systems handled memory above the 6809's 64K address space by feeding the top four address lines into the address lines of a 16x8bit RAM chip creating an address space of 256 4K pages (up to !MB!) that could be mapped into an individual process's address space. It was a cleaver little hack.
I just found this link: https://en.wikipedia.org/wiki/... It's funny because in mentions the Introl C compiler, which I happen to have written.