Nightshade,
You can externally program OBD-2 Honda ECU's threw the diagnostic connector and also OBD-1 Hondata setups. All other OBD-0 and OBD-1 setups must be chipped.

As for the 1994 EX ECU (P0A) all you have to do is remove the Oki 28 pin eprom and replace it with your programed eprom. The P0A already has the CMOS gate, Resistor, Jumper, and Capcitors installed.