this old cheat module for the PSX I picked up a few weeks ago on eBay works and is pretty dang cool? like I don't want it for cheating, I want it to connect a computer to a PlayStation, but it also let's you view the video and audio files on a game disc and listen to what's in the sound buffer and fun stuff like that
Took a few shots for context, it plugs into the parallel port on early-ish PlayStation models and has basically full access to the system from there. And because it also has a parallel port and you can reflash the firmware it can be used as a development tool