PDP-11's existed a long time before Unix was created.
I first started writing code for a PDP-11/40 in 1974 using the Fortran
When the RSX11-D (And the -M , -S and -M-Plus) variants came along the Assembler programme was called Macro-11.
I got hold of the sources to the programme and replaced the PDP-11 instruction set with that of a graphics card that were were using. You could buy a Magtape with all the OS Sources on. The sources also came on microfiche.
MOV R1, R2
I have a full set of PDP-11/34A schematics to go along with the actual hardware in my Garage. One Day I may get around to donating them to the NMOC at Bletchely.
My PDP-11/84 runs RSX11/M-Plus perfectly well to this day.