Genesis Plus is a Sega Genesis / Sega Megadrive / Sega Master System emulator for Wii and GameCube. Additionally a very simple SDL port for Win32 is available too. This is a port of Charles MacDonald’s Genesis Plus, with plenty of improvements.

Changes:

Core/Sound
* added YM2413 emulation in Master System compatibility mode.
* fixed SN76489 noise boost initialization.
* minor YM2612 core optimizations.

Core/VDP
* added accurate emulation of SG-1000, Master System (315-5124, 315-5246) & Game Gear VDP.
* added support for all TMS9918 rendering modes.
* improved Mega Drive VDP timings accuracy in Master System Compatibility mode.
* fixed color palette initialization.
* fixed shifted sprites rendering in Mode 4.
* modified pixel rendering support (pixel depth is now forced at compilation time).

Core/CPU
* optimized 68k core (rewrote 68k interrupt handling, removed multiple CPU types support & unused code) for 5~8% speed improvement

Core/IO
* added accurate emulation of Master System (315-5216, 315-5237, 315-5297) & Game Gear I/O controllers.
* added Terebi Oekaki tablet emulation.
* improved Mouse emulation (fixes mouse support in Cannon Fodder).
* improved Justifier emulation (fixes gun support in Lethal Enforcers 2).
* improved 6-Buttons control pad emulation (fixes Duke Nukem 3D)
* modified lightgun emulation to use common key inputs for all devices.
* 2-buttons controller is now picked by default for Master System games.

Core/MD
* added copy-protection hardware emulation for some new dumped games (Tiny Toon Adventures 3, Mighty Morphin Power Rangers & The Battle of Red Cliffs).
* added Game Toshokan in EEPROM database (verified on real cartridge).
* fixed Micro Machines 2 – Turbo Tournament EEPROM size (verified on real cartridge).
* modified SRAM banswitch hardware emulation to be more compatible with some hacks.

Core/MS
* added Cyborg Z to Korean mapper database.

Core/GG
* added 93C46 EEPROM emulation (Majors Pro Baseball, World Series Baseball & World Series Baseball 95).

Core/General
* added support for .mdx ROM format.
* added Game Gear & SG-1000 ROM support.
* added accurate emulation of SG-1000, Master System (I, II) & Game Gear hardware models for 100% compatibility.
* updated to new Genesis Plus license (see http://cgfm2.emuviews.com/)
* various code cleanup.

Gamecube/Wii
* IMPORTANT: cheats, screenshots & save files are now stored in console-specific directories (ex: /snaps/md, /cheats/ms, /saves/gg, …)
* added 8-bit Action Replay & Game Genie codes support (for Master System & Game Gear games).
* improved audio/video synchronization for PAL games in 50Hz TV modes (now use VSYNC like NTSC games in 60hz modes).
* improved gun cursor positioning accuracy.
* improved horizontal scaling & screenshots rendering in H32 mode.
* fixed a bug with ROM file extension handling that would affect cheats, snapshots, sram & savestate files.
* removed ARAM/injected ROM support (unused).
* removed WPAD_ and PAD_ update from VSYNC callback.
* increased GCC inlining limits for some speed improvment.
* compiled with devkitPPC r24 & libogc 1.8.7.

http://wiibrew.org/wiki/Genesis_Plus