No. Xenix through at least version 2.1 ran on the original IBM PC (and early Xenix was ported to the 68000 (e.g. Tandy model 16), which also lacked hardware VM

No. Xenix through at least version 2.1 ran on the original IBM PC (and early Xenix was ported to the 68000 (e.g. Tandy model 16), which also lacked hardware VM support).[1] You could also run IBM PC Unix in the form of Venix from Venturecom (Version 7 with some BSD things) and PC/IX from ISC (System III). Both were 'official' licensed Unix ports. In the Unix-ish camp, there was Coherent and Minix, as well as various MMU-less Linux projects (e.g. ELKS). And there are many interesting oddballs like iRMX. Yes, OS/2 did require a 286 until it required a 386. If you make virtual memory a necessary attribute to qualify as OS That would be pedantic and historically inaccurate and we shouldn't engage in that. [1] https://gunkies.org/wiki/XENIX https://gunkies.org/wiki/XENIX