On Mon, Jul 04, 2016 at 12:54:15PM -0400, Norman Wilson wrote: Greg Lehey: And why? Yes, the 8088 was a reasonably fast processor, so fast that they could slow it down a little so that they could use the same crystal to create the clock both for the CPU and the USART. But the base system had only 16 kB memory, only a little more than half the size of the 6th Edition kernel. Even without the issue of disks (which could potentially have been worked around) it really wasn't big enough for a multiprogramming OS. ===== Those who remember the earliest UNIX (even if few of us have used it) might disagree with that. Neither the PDP-7 nor the PDP-11/20 on which UNIX was born had memory management: a context switch was a swap. That would have been pretty slow on floppies, so perhaps it wouldn't have been saleable, but it was certainly possible. In fact Heinz Lycklama revived the idea in the V6 era to create LSX, a UNIX for the early LSI-11 which had no memory management and a single ca. 300kiB floppy drive. It had more memory than the 8088 system, though: 20kiW, i.e. 40kiB. Even so, Lycklama did quite a bit of work to squeeze the kernel down, reduce the number of processes and context switches, and so on. Here's a link to one of his papers on the system: https://www.computer.org/csdl/proceedings/afips/1977/5085/00/50850237.pdf I suspect it would have been possible to make a XENIX that would have worked on that hardware. Whether it would have worked well enough to sell is another question. Norman Wilson Toronto ON