This is what my colleague Stephen Schenck does with FPGA cartridges from Everdrive. This allows him to play games on a CRT television for the most authentic retro experience possible. Ryan Haines ...

[Hoglet67] has released a very interesting set of FPGA designs that allows a small board sporting a Xilinx Spartan 3 to add a 6502, a Z80, a 6809, or a PDP/11 to a BBC Micro via the tube interface.

And if you’d like to get even deeper into the weeds you can design your own computer including the instruction set completely from the ground up using an FPGA. This project, called the Moncky ...