To add to this I didn't do a function-pointer jump table. A function pointer jump table was too slow and involved multiple look-ups. I took the opcode of the 65

To add to this I didn't do a function-pointer jump table. A function pointer jump table was too slow and involved multiple look-ups. I took the opcode of the 6502 or Z80 instruction, shifted it, then added that value to the PC (program counter) register. The new value in the program counter was effectively the goto. All the assembly functions that handled each opcode were aligned on a multiple of powers of two value, 2048 bytes IIRC. Though it might have been 1024 bytes, this is over 25 years ago. The instruction immediately after the PC write set the the return address for the function about to be called, the return address write worked due to the pipelining in the MIPS CPU. The return address was the instruction immediately after the PC write. The opcode function executes, and then returns back to the write instruction, which then falls through to the no-op (opcode zero), which handled the gathering of the next opcode to be processed, any updates to the display and hardware, cleaned up the stack, and then looped to process the next opcode.