Writing an alternative Mac Plus core for a pre-existing Amiga or Atari ST-in-an-FPGA board would be one way to go, but seems less fun, since I like to build stuff with my hands. Nevertheless I'm starting with this Spartan 3A board (and soon an Altera DE1 board) that's not too different from those Amiga boards, because it's the easiest way to get started. Once things are mostly working there, I plan to create a custom board that eliminates any uneeded parts, adds vintage keyboard/mouse/floppy connectors, and incorporates any daughterboards I made for a microcontroller or other stuff. At that point it would also be possible to extract the 68000 and maybe VIA out of the FPGA, and add them back as real chips for extra style points.

It's basically a huge pile of electronic tinkertoys that can be interconnected according to a "meta-code", VHDL or Verilog, that has nothing to do with the normal operation of the chip once it's programmed. (Once the FPGA is programmed it's not "emulating" the chips it's coded for, it in essence *is* the chips.)

Click to expand...

That's a good way of putting it. The Verilog code determines the configuration of 40-bazillion internal interconnections between 20-bazillion primitive logic gates on the FPGA. The configuration data is like a tremendous number of switches, or like the plugboard configuration panel on early computers like Univac. Each switch can either connect two specific wires inside the FPGA, or leave them unconnected. After that, it's the same as if you'd soldered up all those primitive logic gates by hand, and it really *is* the chip described in the Verilog code. This stuff is fascinating, and if you're into digitial electronics, it's like sex on a stick. And to trag's question, I'm pretty certain the TG68 68000 core I got from opencores.org is reverse-engineered from the known behavior of the real 68000.