Instructables user [dany32412] recently built what is arguably one of the smallest NES consoles we have seen to date. Using a Nintendo on a Chip (NOAC) board, he has fabricated an NES system that fits inside a hollowed out NES cartridge.
He purchased a NOAC system at a local resale shop and got to work disassembling it. As most of these devices typically consist of a game system built into the controller with a Famicom game slot added for good measure, he knew he had a lot of work ahead of him if he was going to convert it to work properly with actual NES games and controllers.
He hacked apart most of the NOAC’s board, leaving just the CPU and the controller interface chip. He then built a custom controller interface board in order to properly map his NES controller’s buttons to the pads on the NOAC. He wired in a 72-pin NES cartridge slot, then added a pair of controller ports and a power switch. Once he had everything connected and tested, it was all secured in a Super Mario Brothers NES cartridge.
Check out the video below of his mini NES in action.