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 Microsoft wound up getting partial ownership of (old) SCO for what I'd understood to be non-payment of bills. I don't think it was ever more than 1/3rd. 

 The first port of Xenix 8086 was to Altos.   Altos had several machines which implemented this hardware configuration.  There were a couple of compatible versions called, I think, 8600 and  586.  this had an 8086 CPU connected to a Memory Management Unit (MMU) which allowed a level of demand paging.  it didn't support pagefaults or any such niceties but it did allow a reasonable level of swapping. Real mode 8086 doesn't support any of this. I don't think it had a general bus but it did support an 8087 and extra memory.   The port was done in late 1980 and early 1981 by Gordon Letwin and the first version shipped in the Autumn of 1981.  The second port was also done by Gordon in late 1981 for Intel.  The first prototype we got from Intel had a square front about a foot on a side and was about 20 inches deep.  I can't remember what it was called, but it had an 8 inch floppy drive oriented vertically, in addition to the internal hard disk.  it was built around a Unibus backplane.  by early '82 it had been replaced by a similar box using 5" floppies and I think a 20MB hard disk in the same cubic format, and a couple of years later a flatter white box more typical of the desktop configurations of the era.   

 The first SCO real mode port of xenix didn't come along until 1983two years after Gordon's originaland it didn't work well for more than a year after (or ever, reallyit's unmapped 8086...).  By this point the 286 was available, which had a real memory map on the chip, so there was little point in continuing with 8088 or 8086 real mode.  (a memory map helps several things: it allows more physical memory to be available than the address space of the machine (1MB in the case of the 8086, and only 640K on the PC).  It allows each app to have its own address space, which makes it more practical to run multiple of them, and it keeps errant pointers from being used to trash the running kernel or other apps).   the macintosh and real mode windows imposed fairly onerous constraints on applications to allow very limited (and flakey) multitasking, and the SCO real mode port wound up doing something similarnamely "small" and "medium" model apps. 

 Most of the system and support was done by the Microsoft Xenix group through this period1980-87 or so.  SCO, Altos, Tandy and the others maintained or updated ports which were /started/ at microsoft.  /NOT/ the other way around. 
    -Hans, Xenix Compiler guy