Sega G80

Sega G80
Manufacturer: Sega
Release Date RRP Code

The Sega G80 is an arcade system produced by Sega in 1981. It can be considered a successor to the Sega VIC Dual system, and was Sega's arcade platform of choice before the release of the Sega System 1.

The G80 was designed to be a more versatile system than those seen in arcade cabinets of the past. Rather than rely on bespoke cabinet designs for each game, Sega opted for a more cost-effective "Convert-a-Game" system (as it was marketed in the US), in which games housed on CPU boards could be easily swapped by arcade operators. It also marks Sega's recognition of the likes of Atari's Asteroids and Lunar Lander, as two variants of the G80 system exist - one which displays raster graphics, and another that displays color vector graphics.

The G80 gets its name from its CPU - a modified Z80 processor (which is attached to each game). The G80 is largely identical to the Z80, however the "ld (address),a" instruction (opcode 32h) was modified to mangle the address written to — an early form of copy protection. The mangling system is rather complicated, and differs from game to game.

The Sega G80 platform provided a basis for many reasonably successful vector-based games from the company, some of which, such as Space Fury, Tac/Scan, and, perhaps most famously, Star Trek: Strategic Operations Simulator, saw home console/computer ports.

Technical Specifications

• Board composition: One board
• Main CPU:
  • Raster: Zilog Z80 @ 8 MHz (8-bit & 16-bit instructions @ 1.16 MIPS)
  • Vector: Zilog Z80 @ 3.86712 MHz (8-bit & 16-bit instructions @ 0.561 MIPS)
• Sound boards:
  • Sega USB (Universal Sound Board)
    • MCU: Intel i8035 @ 3.12 MHz (8-bit instructions @ 3.12 MIPS, 1 instruction per cycle)
    • Sound chip: Sega Melody Generator (programmable sound generator)
  • Speech Board (optional)
    • MCU: Intel i8035/i8039 @ 3.12 MHz (8-bit instructions @ 3.12 MIPS)
    • Speech synthesizer: General Instrument SP0250 (linear predictive coding)
  • Sega System 1 sound board (optional, used for Sindbad Mystery in 1983)
    • Sound chips: Sega SN76496 @ 4 MHz, Sega SN76496 @ 2 MHz
• Raster graphics board: Sega Video I
  • Raster display controller: Sega Raster Display Controller @ 15.468 MHz
  • Video resolution:
    • Horizontal: 256×224 (display), 328×262 (overscan)
    • Vertical: 224×256 (display), 262×328 (overscan)
  • Color palette table: 256 (8-bit RGB PROM)
  • Colors on screen: 64 to 128 (palette RAM)
  • Tilemap planes: 2 layers, horizontal and vertical scrolling, 8×8 tiles, 4 colors per tile
  • Sprite capabilities: 28 to 32 sprites per scanline, 224 to 256 sprite pixels/texels per scanline, 4 colors per sprite, 8×8 to 16×16 sizes
• Vector display controller: Sega Display Controller
  • Color depth: 64 (6-bit RGB)
• RAM:
  • Default: 10 KB (2 KB main, 8 KB video)
  • Monster Bash: 20 KB (4 KB main, 16 KB video)
  • Sindbad Mystery: 22 KB (4 KB main, 16 KB video, 2 KB sound)

List of Games

Raster

• 005 (1981)
• Astro Blaster (1981)
• Space Odyssey (1981)
• Monster Bash (1982)
• Pig Newton (1983)
• Sindbad Mystery (1983)

Vector

• Space Fury (1981)
• Eliminator (1981)
• Battle Star (1982)
• Star Trek: Strategic Operations Simulator (1982)
• Tac/Scan (1982)
• Zektor (1982)

Sega arcade boards
Originating in arcades
77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 VIC Dual G80 Zaxxon VCO Object System 1 LaserDisc Appoooh Hang-On System 2 System 16 OutRun Gigas X Board Y Board System 24 System 18 System 32 Model 1 Model 2 H1 Board Model 3
Console-based hardware
84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 SG-1000 System E System C Mega-Tech System Mega Play Sega Titan Video NAOMI Hikaru NAOMI 2 Atomiswave System SP Chihiro Triforce
PC-based hardware
05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Lindbergh Europa-R RingEdge RingWide RingEdge 2 Nu Nu 1.1 Nu 2 ALLS