The Nimbus used in the C demonstration seems to be a 16bit 80186 computer. It runs DOS but is not PC compatible. https://en.wikipedia.org/wiki/RM_Nimbus
https://en.wikipedia.org/wiki/Tandy_2000
The Mindset was another, that languished in obscurity until a cache of them were found at Computer Reset:
https://en.wikipedia.org/wiki/Mindset_(computer)
The 186 had on-chip stuff (timers, an interrupt controller, and so forth) at I/O addresses where the PC had different stuff offboard, thus precluding the possibility of a 100% PC compatible 186 machine. So there were a few interesting, not-quite-PC DOS machine designs running a 186 out there.