I thought Xenix was SCO.Back in those days Microsoft had their own flavour of Unix, remember Xenix?
Back in the early nineties Unix was hailed as the great white hope of interoperability between machines.
I worked for an American software company at the time. We supported HPUX, DEC Ultrix, IBM AIX, SCO Xenix plus a few others. All different.
Interoperability my arrse.