Recall Arithmetic: The haves and have-nots

[Didier Lachieze]

(05-22-2019 09:33 AM)[kby] Wrote:  Can’t really buy that explanation for the -65. Storage arithmetic is not merged so it would not be odd to have recall arithmetic unmerged.

Well, with unmerged recall arithmetic it takes one more step compared to standard recall. For example: RCL + 2 is 3 steps, while RCL 2 + is 2 steps because RCL 2 is a partially merged instruction.
Without recall arithmetic you loose the T-register, but does it justify the full implementation of recall arithmetic? I would say that during the design of the HP-65 (the first programmable pocket calculator) the designers may not have seen any advantage to implementing recall arithmetic.