Hi,
  The GI CP-1600 16-bit CPU had an architecture
very similar
to the PDP-11, but used a 10-bit instruction word. I think
GI even marketed 10 bit ROMs. These were used in various
incarnations as the CPU in many Activision consoles. 
 They were used in the various "Intellivision" consoles....
 That's a machine I'd like to have a play around with (as in
 programming), but I'm having too much fun with the Vectrex right now. ;-) 
I wrote code for the CP-1610 at some point in the past, but I don't
remember where or when.
Peace...  Sridhar