Master System:FM Audio Information



The Sega Mark III was a console launched in Japan in 1985 that was the initial version of the Sega Master System hardware. It was essentially a heavily upgraded SG-1000, featuring a new graphics chip and increased RAM. However, the Mark III still used a derivative of the Texas Instruments SN76489 PSG chip used in that earlier console, which was beginning to show its age by 1985. To rectify this, Sega released an audio expansion in 1987 known as the FM Sound Unit, which connected to the Mark III's expansion port and mixed the console's audio signal via a 5-pin DIN cable. This expansion was based around a Yamaha YM2413 FM synthesizer chip, which was also utilized in several arcade games, consumer-level music keyboards and an MSX audio expansion. Though this chip massively expanded the Mark III's audio capabilities, it was not as sophisticated as the YM2612 later used in the Sega Genesis/Mega Drive and was not fully programmable in terms of instrument patches.

Supported Games
A large number of games released from 1987 to 1989 feature FM audio capability, even on Western releases despite the FM Sound Unit never being released or featured in any hardware outside of Japan. This is because Sega used the same ROM file for these games across regions, so the FM audio code remained intact.

Officially Supported
These are games which were released in Japan and explicitly advertised support for the FM Sound Unit. The international versions of these games also still retain FM support with a couple of exceptions.

Unofficial Support
These are games which will support a detected FM Sound Unit, but this was not explicitly advertised as these games were released outside Japan where the FM audio hardware was unreleased.

FM Audio on Real Hardware
There are several methods that allow you to play your SMS games on original hardware with FM sound. Some require console modifications and others do not:

Mark III with FM Sound Unit
One of the easier (albeit one of the most costly) options is to simply use an original Sega Mark III with the FM Sound Unit. However, this setup has a number of caveats, the chief of which is that the Mark III is incompatible with Western SMS cartridges due to their different shape and pinout. This can be remedied by acquiring a suitable cartridge adapter. These cartridge adapters are readily available from Aliexpress or eBay, but these leave the cartridge sticking up high from the console and can cause a faulty connection if accidentally bumped or touched. Another issue is that the FM Sound Unit does not pass through RGB so composite video is the only video output option for a stock setup. It is possible to modify the FM Sound Unit with an 8-pin DIN pigtail cable and swap the original 5-pin DIN jack with an 8-pin jack. But as with any physical modification, there is always the slight risk of accidental damage and considering the rarity of the FM unit, this is a modification best left to someone with experience.

Another issue is that the Mark III/FM Sound Unit combination does not mix together both FM and PSG audio. This is especially apparent with the FM audio hack of Sonic the Hedgehog which uses the YM2413 for music and PSG for sound effects.

SMSFM Mod
Tim Worthington sells an FM kit that can be installed in an SMS console. Installation in an original SMS is fairly simple, as it plugs directly into the rear expansion port, requiring only three wires to be soldered for the FM audio to be mixed with the internal PSG audio. The kit can also be installed into a Master System II, either via wiring the kit directly into the motherboard or by using a special adapter from Consoles Unleashed. There have also been reports of people installing this kit into a Power Base Converter, or even a Genesis/Mega Drive itself, but no instructions for that are available. These methods also involve wiring the kit directly into the host console's motherboard.

Power Base Mini FM
The Power Base Mini FM is a cartridge converter designed by dB-Electronics for the Genesis/Mega Drive which provides backwards compatibility with SMS cartridges, complete with additional FM audio through an onboard YM2413. This will also work with SMS flash carts such as the Master Everdrive.

Japanese SMS/MK-2000
Another option is the Japanese Sega Master System console (model number MK-2000), which has a YM2413, 3D glasses adapter and rapid fire module all built into the console itself. These were all separate add-ons for the Mark III. However, the Japanese SMS is not compatible with non-Japanese cartridges and will require a cartridge adapter for these games. These cartridge adapters are readily available from Aliexpress or eBay, but these leave the cartridge sticking up high from the console and can cause a faulty connection if accidentally bumped or touched.

Another solution for the JP SMS is the SMS Gender Adapter, which connects to the expansion port at the rear of the console. Though this provides a cleaner solution for playing Western cartridges, it does have some compatibility issues with certain games and flash carts.

Genesis/Mega Drive Flash Carts with FM Support
Several Genesis/Mega Drive flash carts such as the Mega Everdrive Pro, Mega Everdrive x7 and Mega SD can provide FM audio through FPGA emulation of the YM2413, the output of which is then routed into the Genesis/Mega Drive. This is probably the most feasible solution for those who play Master System games via a Genesis/Mega Drive and want to experience FM audio on compatible games.

https://youtu.be/ayKxnrYCpPI

NEO Myth Cartridges
In addition, there is another flash cart known as the NEO Myth MD 3in1 which, like the Power Base Mini FM, has an actual YM2413. The same company also produced a Master System variant which again, also features a real YM2413. Unlike the Genesis/Mega Drive cartridge, this requires the SMS's audio output to be mixed into the cartridge since the SMS does not have an audio input on its cartridge port. This is not unlike the original FM Sound Unit, which had a hardwired cable to mix in audio and pass through video from the attached console.

Using the enhanced menu's is a must, as the stock menu's are terrible: Genesis cart enhanced menu: (1st post):  http://www.neoflash.com/forum/index.php/topic,5880.0.html **SMS cart enhanced menu:** http://www.neoflash.com/forum/index.php/topic,7199.0.html

The Neo carts are _not_ plug-and-play like the Everdrives, they actually require software to read and write ROMs. You can purchase an additional MicroSD card adapter, but it's expensive and you'll still need the software for initial setup (although after setup is complete, you can just read and write ROMs like a normal ROM cart):  http://www.ic2005.com/shop/product.php?productid=33&cat=3&page=1

Comparison of the above methods:


 * An outdated video demonstrating the differences between the above choices. It also includes an audio analysis section on the Mega Everdrive Pro: http://www.retrorgb.com/files/MK-2000-FMKit-NeoSMS-NeoMD.wav