"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.