The Sega Master System (commonly referred to as the SMS) was an 8-bit third-generation video game console that was made by Sega and released in 1985 in Japan, 1986 in the US and 1987 in Europe. The Sega Master System was Sega's competitor to the NES by Nintendo. Not only did the SMS take cartridges, but small cards as well. While the graphics were particularly better on the Sega Master System than the NES, the NES had a better sound chip. Later, the Sega Game Gear was released, which was essentially a portable Sega Master System that competed with Nintendo's GameBoy. Sega's mascot got his first debut on the Master System, Sonic the Hedgehog, who is basically Sega's equivalent of Mario.
Sega Master System Plus
A standard Sega Master System but with a built-in game.
Sega Master System II
A shorter Sega Master System, which was the equivalent to the toploader NES, except it was only released in Europe.
The Japanese version of the Sega Master System. This was a different looking console than the US and PAL SMS and had different controllers. Like the Famicom Disk System, Sega created a floppy disk drive for the Mark III but it was never released.
Music and Sound
Sega had licensed the Texas Instruments SN76489 chip and included it inside the VDP (Video Display Processor) Custom Chip of the Master System. Depending on the version the physical chip is either called 315-5124 (SMS1) or 315-5246 (SMS2). Aside from Graphics, the chip can output 3 channels of squarewaves as well as a white noise channel. Features include volume control for each channel as well as an Envelope Generator for each instrument.
The Japanese Model of the Master System also had an additional Yamaha YM2413 FM Synthesis chip that can work in 2 different modes. In the first it can play up six FM channels as well as five channels with predefined percussion instruments, and in the second mode it can play nine FM channels but no percussion, just like AdLib Visual Composer.
This sound hardware can also be found in several other Sega Systems like the Game Gear which also uses the VDP, although modified to offer stereo sound, or the Mark III, which had a YM2413 based FM Sound Unit available as add-on hardware.
The Master System's sound chip can go from frequency $3FF to $00.