That new core sounds very exciting. Keep us in the loop as to how it is progressing!
Well, right now I am testing the core against the musashi 68k emulator from mame. So far, I have tested all the flavors of ADD, SUB, shift and rotate plus the MOVE, LEA, JSR, BSR and RTS. On average the 90 MHz core runs like a 30MHz 68000.
The core is designed to be small (currently : 1700 LUTs), so it is heavily microcoded (more than the original 68000).
The microcode is Forth based and quite small (~6KB), to prgram the microcode ROM, I had to create my own microcode assembler with Lex and Yacc.
Later, I will create a more powerful design by having a true 32-bit ALU, a separate effective address ALU and the fetch/decode done in parallel.
If I move to a faster FPGA architecture, I think I can reach 150 MHz.
It is really fun to re-create a 68000 from scratch.
Regards,
Frederic