The idea: to use an Arduino as “boot ROM”. Here is a 68008 version. First it simulates some instructions, used to write basic loader to the RAM.
Another “Retrocomp in a FPGA” approach, this time for Atari ST(E): Suska. Based on Altera FPGA, boosted by a lot of circuits (Memories, some ATmegas, Ethernet chip…) You can build your own, or simply buy ready made board. Author says: “At the very beginning it was just the address decoder of the GLUE custom chip which was replaced by a simple model. That was back in February 2003. Many hundreds of hours later all custom chips found in the Atari ST have been replaced with a single FPGA. Even the 68000 CPU has been integrated.”