Comment by snvzz
7 hours ago
m88k is an ISA primarily designed by Mitch Alsup.
Mitch Alsup has extensive experience in ISA design, has participated (tangentially) in informing RISC-V design process.
Recently, he's designed my66000, an interesting, fresh take at a new ISA that I recommend exploring.
Alsup liked to write a lot about his my66000 on Usenet, but does not share documents about it with everyone. (Yes, I've emailed him and been ignored. I have had to piece together what I know about it from multiple posts.) Apparently it runs in FPGA and there are assemblers and compiler back-ends for it.
Like the 88000, the register file is shared between integer and floating point units. One interesting detail is that it supports CRAY-style vector operations using the same architectural registers, and downgrades to scalar operation automatically on interrupts. This means that the register state to load/store on context switches is small.