Sega Mark III

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Sega Mark III
Manufacturer: Sega
Variants: Sega Master System
Add-ons: Demo Unit II, Telecon Pack, FM Sound Unit
Release Date RRP Code
Sega Master System
¥15,00015,000[3] SG-1000M3[2]
Sega Master System
Sega Master System

The Sega Mark III (セガマークIII) is a video game console created by Sega. It is the successor to Sega's earlier SG-1000 II (itself a redesigned SG-1000), and was released in October 1985 in Japan, before being distributed in South Korea and Taiwan later in the decade. No models of the Mark III were released outside of Asia, but the console did form the basis of the Sega Master System which was distributed internationally.

The Mark III stands as Sega's second attempt at capturing a share of the Japanese video game market in the face of the Family Computer (Famicom) created by Nintendo, sporting significant upgrades over its predecessors. The technology was used as a foundation for its successor, the Sega Mega Drive.


The Mark III is built similarly to the SG-1000 II, so much so that to the untrained eye, it is easy to mistake one for the other. It is a long, white system sporting a cartridge slot, a card slot, and two DE-9 controller ports at the front of the unit. On the left lies an expansion port, later utilised by the FM Sound Unit, and in addition to the RF television output, an 8-pin A/V port, giving greater picture quality than the system's predecessors. Like the SG-1000 II (and Famicom), controllers (now SJ-152s) can be docked on either side of the unit.

The Mark III offers two major upgrades over the SG-1000 (with the optional FM Sound Unit bringing enhanced sound) - superior visuals offered by a new video display processor, and more RAM. Generally this is represented by twice as many on-screen colours and sprites, and smoother scrolling - everything else is largely the same as the SG-1000. The upgrade puts it ahead of the Famicom in many regards, although without the FM Sound Unit, the Famicom has technically superior sound capabilities (furthered still by the Famicom Disk System add-on).

The system is backwards compatible with earlier SG-1000 titles, both in terms of cards and cartridges, and likewise, the controllers are interchangeable. Cartridges and cards are the same physical shape as their SG-1000 counterparts, but will not function in an SG-1000. Sega also released the Telecon Pack, allowing the Mark III to connect to a television wirelessly.

In the early days, the Mark III was marketed as an upgrade to both the SG-1000 and SC-3000, with accessories such as the Sega Keyboard, 4 Color Plotter Printer and Data Recorder SR-1000 even mentioned on the console's box as parts of a "complete" system. Few, if any Mark III games make use of these peripherals - whereas the diagrams suggest Mark III games could have been distributed on compact cassette, none were, likely as no Mark III-enhanced BASIC interpreters (or other operating systems) were ever released.

The Sega Mark III was redesigned as the Sega Master System for release in other markets. This was mainly a cosmetic revamp; the internals of the console remained largely the same. The redesigned console was itself released in Japan in 1987, but with the features of the FM Sound Unit built in as well as a 3-D glasses port and a built-in Rapid Fire Unit.


Main article: Master System consoles in Asia.

Technical specifications

See Sega Master System technical specifications.


  • Instruction set: 8-bit instructions
  • Clock rate: 3.579545 MHz


  • Graphics processor (GPU): VDP (Video Display Processor), derived from TMS9918
  • Screen resolutions: 256x192 and 256x224 pixels
  • Color palette: 64 colors
  • Simultaneous colors on screen: Up to 32 (64 using programming tricks)
  • Sprites: Up to 64 sprites on screen
  • Sprites pixel sizes: 8x8 or 8x16 pixel sprites
  • 8x8 pixel characters, max 488 (due to VRAM space limitation)
  • Horizontal, diagonal, vertical, and partial screen scrolling


  • 3 sound generators, 4-10 octaves each
  • 1 white noise generator


  • System RAM: 24 KB
  • Main RAM: 8 KB
  • Video RAM (VRAM): 16KB


  • The Sega Mark III does not have a BIOS ROM
  • Game card slot



Sega's first console, the SG-1000, launched on the same day as the Famicom in Japan, and was, like many other systems of the era, decimated by Nintendo's efforts. Its computer sibling, the SC-3000 was met with more open arms (including in some Australasian and European markets), but by 1985 it was clear that support for Sega's systems were drying up. Nevertheless, Sega's attempts were at the very least notable - whereas other rival systems of the day had been struck off within a year of the Famicom's launch, Sega held a strong, albeit distant, second place in Japan, prompting the company to push forward with a more powerful alternative - the Sega Mark III.


The Mark III was released in Japan on October 20, 1985, with its main competition again being the Family Computer. Despite being a cartridge-based system, for the first eight months, no traditional cartridges were produced, with the library instead being populated by cost-reduced Sega Cards. The release of Fantasy Zone ushered in a new phase of cartridge production, and support lasted until February 1989, ending with Bomber Raid.

Over one million units were sold in Japan during Mark III's first year, but similar to its predecessors, the Mark III was unable to dethrone Nintendo or win considerable support from the gaming public. The situation is said to have been an improvement over the SG-1000/SC-3000's fate, but even with superior system specifications, Mark III sales paled in comparison to the Famicom's. By 1989, the Sega Mark III had sold over 1.7 million units in Japan.

Sega published every Mark III game internally with the exception of two, Argos no Juujiken and Solomon no Kagi: Oujo Rihita no Namida by Salio.


In Taiwan, Aaronix distributed the Mark III, having previously brought the SG-1000 II to the region.

South Korea

The Mark III was distributed in South Korea from November 1988 by Korea Oacs and HiCom with help from Samsung, and was the first Sega console to be sold in the country. Sega planed to produce 50,000 units in 1989[5], but plan was abolish after Samsung released Gam*Boy in April 1989 and all new software was labelled as compatible with Mark III/Gam*Boy.


List of games

Main article: List of Master System games.

Launch titles


Production credits

Developer mentions[6][7]

Magazine articles

Main article: Sega Mark III/Magazine articles.

Promotional material

External links


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Topics Sega Master System | Technical Specifications (Hardware Comparison) | History | Boot ROM | Magazine articles | Promotional material | Merchandise
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Add-ons Demo Unit II | Telecon Pack | FM Sound Unit | 3-D Glasses
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Misc. Hardware Action Replay | Card Catcher | Action Case | Freedom Connection | Playkit
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