Recall Arithmetic: The haves and have-nots

[Dave Britten]

(05-24-2015 01:27 AM)Paul Dale Wrote:  The 25 has the opcode space for recall arithmetic.


Pauli

It does have the space, but I wonder if the way instructions are decoded and executed limited them. Note how all the GTO and STO instructions tend to be aligned in such a way that looks like it was intended to ease decoding the address. Perhaps there wasn't enough ROM space to handle more complex address decoding for recalls, or just not enough ROM space to handle any recall arithmetic period.

If it's an alignment issue, one has to wonder why they wouldn't have just moved other instructions around, though. Anybody have any insights into this from looking at a 25 ROM disassembly?