Really? I though OS/2 was on the 386. I thought that the 286 had some limit on the size of a process, but you could execute multiple processes. I don't know why, but I think it was 64k per process. Also, the other thing I recall was thinking that it was a nice idea.
I was only familiar with 68k so I'm probably wrong here.
The 286 is a 16-bit CPU so there would have been various
memory limits. http://www.os2museum.com/wp/?page_id=313 has some details on what it can do, but not much mention of limits...
Actually looks like Xenix used that too. http://www.tenox.net/docs/microsoft_xenix_30_286_press_relea...