Why not using Hitachi's 6309? https://en.wikipedia.org/wiki/Hitachi_6309 https://en.wikipedia.org/wiki/Hitachi_6309 It has two 8-bit accumulators, A and B, an

Why not using Hitachi's 6309? https://en.wikipedia.org/wiki/Hitachi_6309 https://en.wikipedia.org/wiki/Hitachi_6309 It has two 8-bit accumulators, A and B, and they can be treated as a single 16-bit accumulator, D. It has two 8-bit accumulators: 'E' and 'F'. These can be concatenated to form 16-bit accumulator 'W'. The D accumulator can be concatenated with W to form 32-bit accumulator 'Q'! Two 16-bit index registers X and Y Two 16-bit stack pointer U and S Transfer register 'V' to speed up inter-register instructions. A 8-bit register, DP, to set the base address of the direct page. 8/16-bit Zero register '0' to speed up operations using a zero constant. This register always reads zero and writes to it are ignored.