"Yes, all of the Xerox Workstations from the Alto on use a Mesa processor,
A little like a Nova but with Writable Control Store (WCS)."
Completely false.
One of the Alto instruction sets was an extended Nova. The MESA machine
is more like an HP3000 than a Nova. It is defined in the MESA "Princeops"
manual. Alan Freier had this on line at one point, not sure if anyone
saved a copy.