http://code.google.com/p/genplus-gx/wiki/FeaturesSupport for various peripherals
•2-buttons, 3-buttons & 6-buttons Control Pads
•Sega Team Player & EA 4-Way Play multitaps
•Sega Mouse
•Sega Paddle Control
•Sega Sports Pad
•Terebi Oekaki
•Sega Light Phaser
•Sega Menacer
•Konami Justifiers
•Sega Activator
•XE-1AP analog controller
Support for various cartridges extra hardware
•SVP DSP (Virtua Racing)
•J-Cart adapter (Micro Machines & Pete Sampras series, Super Skidmarks)
•Backup RAM (max. 64KB)
•I2C (24Cxx), SPI (95xxx) & MicroWire (93C46) EEPROMs
•RAM cart (max. 512KB) (Sega/Mega CD)
•“official” ROM bankswitch hardware (Super Street Fighter 2)
•“official” backup RAM bankswitch hardware (Phantasy Star 4, Legend of Thor, Sonic the Hedgehog 3)
•all known unlicensed/pirate cartridges bankswitch & copy protection hardware
•all known Master System & Game Gear cartridge “mappers” (incl. unlicensed Korean ones)
•Game Genie & Action Replay hardware emulation
•Sonic & Knuckles “Lock-On” hardware emulation
•support for ROM image up to 10MB (Ultimate MK3 hack)