"Avalonian" - just like King Arthur I'll be back when you need me. Er...

Why not try compiling some C for a couple of subroutines that reflect your application for an alternative RISC machine ? I suggest you download a free toolchain such as CodeSourcery G++, find out how to select compilation for an earlier ARM CPU, switch on every optimisation possible and see what comes out in the mixed lising, maybe get some ideas ? If that is not to your taste maybe there is another RISC as resource-absent as the CPD1802 you could do something similar for ? Not sure how old the CPD1802 C compiler is...I could always hammer a compiler with a.n.other assembler for smaller chips but I wouldn't be so sanguine in the face of recent compiler advances... If that doesn't work maybe there is a fully static CPD1802 model in VHDL you could pop into a fast small FPGA and generate your own CPU running at warp speed and hence making your execution problems vanish - faster bus-interfacing problems aside, that is... What is your application anyway ? Is the CPD1802 the only non-Intel chip licensed for space flight ? What is wrong with an ARM Cortex-based microcontroller ? Was Rick Deckard really Nexus 6 ? Anyway, the best of luck with your project, I hope you have a lot of fun solving your puzzles and get a great result.