SG-1000 Mark III
Manufacturer SEGA
Type Video Game Console
Origin Japan
First Available Oct. 1985
Discontinued 1987
Media Cartridge
Units Shipped ?
Predecessor SG-1000 Mark II
Successor Master System

History & Development

The Mark III was released in Japan on October 20, 1985 to compete with the Nintendo's Famicom, following on from the SG-1000 Mark I and SG-1000 Mark II. The Mark III was built similarly to the Mark II, with the addition of improved video hardware and an increased amount of RAM.

The system is backwards compatible with earlier SG-1000 titles. As well as the standard cartridge slot, it has a built-in slot for "Sega Cards", which are physically identical to the cards for the Sega SG-1000 "Card Catcher" add-on.

The Mark III was redesigned as the Sega Master System for release in other markets. This was mainly a cosmetic revamp; the internal components of the console remained virtually the same. The redesigned console was itself released in Japan in 1987, but with the addition of a built-in Yamaha YM2413 FM sound chip (this had been an optional extra on the Mark III), Rapid Fire Unit, and 3-D glasses adapter.

Sega Master System game cartridges released outside Japan had a different shape and pin configuration to the Japanese Master System/Mark III cartridges. This may be seen as a form of regional lockout.

Neither the Mark III nor the Japanese Sega Master System were commercially successful, due to strong competition from the Nintendo Famicom. The final Japanese game release was Bomber Raid, on February 4, 1989.


  • CPU Z-80A (4MHz)
  • Memory
    • ROM Options 8KB to 48KB (sold separately)
    • RAM Home 8KB using BASIC (24 KB optional)
    • VRAM 16KB
  • Video Processor:
    • VDP (Video Display Processor) derived from Texas Instruments TMS9918
    • Up to 32 simultaneous colors available from a palette of 64 (can also show 64 simultaneous colors using programming tricks)
    • Screen resolutions 256x192 and 256x224
    • 8x8 pixel characters, max 488 (due to VRAM space limitation)
    • 8x8 or 8x16 pixel sprites, max 64
    • Horizontal, diagonal, vertical, and partial screen scrolling
  • Sound (PSG): Texas Instruments SN76489
    • 4 channel mono sound
    • 3 tone generators, 10 octaves each, 1 white noise generator
    • Sound (FM): Yamaha YM2413
    • 9 channel mono FM sound available as plug-in module for Mark III built into Japanese Master System supported by certain games only
  • Ports
    • Slot × for card 1
    • Slot × for cartridge 1
    • Slot edge connector ×1 for expansion
    • RF output (home TV antenna terminal)
    • Video output (dedicated video cable is required)
  • Power / Power Consumption
    • DC9V/7.7W (AC Adaptor)
  • Dimensions
    • Width - 318 mm
    • Depth - 145 mm
    • Height - 52 mm






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