The NPDP Reader is a odd looking GameCube console which was used mainly for alpha and beta testing.
It can load review copies of games from a NPDP Cartridge which is a hard disk based slot loading cartridge that can fit 4 games on it. Games are selected via a slot selector on the console made up of 4 LEDs and a slot selecting button. Disk eject and disk errors can be simulated by buttons provided on the console in front of the NPDP Cartridge slot.
Apart from that, it is very standard internally and 100% of the cartridge reading hardware is embedded in each cartridge.