Do you have a cite that states that the PIC1640 is a
direct
descendent of the SMS 300?
That seems highly unlikely. The PIC was being worked on at GI on
Long Island when I was doing a project for GI in the late 70's
on a CP-1600 system. The designers were Scottish. I tried to convince
them to make the architecture more like the 1600's (ie. PDP-11 like)
because I thought the 11 was a better architecture than what they were
coming up with.