> The device in question is the gameshark. > > There were 2 versions. The one where you would pop a disc in and do a swap after > loading and had a lockout fob (memorycard?). > > The other device (which you are thinking of) which plugged into the parallel port on > the back (which was removed in later versions of the psx). > > http://en.wikipedia.org/wiki/GameShark#PlayStation_GameShark_Pro
There was also Action Replay (Datel) which you plugged into the parallel port of the PSX. I still have one around here somewhere...