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Sega X Board

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Fast facts on Sega X Board
Manufacturer: Sega
Release Date RRP Code
Arcade
JP
1987-07-17 ¥?  ?
Arcade
EU
1987-10 £?  ?
Arcade
World
1987  ?


The Sega X Board is an arcade system board released by Sega in 1987 as a successor to Sega OutRun hardware. It debuted with After Burner and Thunder Blade.

The X Board specification is an expansion of the OutRun hardware, with more memory, and a more powerful GPU chipset, allowing for twice as many sprites/textures on screen at once, twice as many tile layers, a faster fillrate, more colors, and sprite/background rotation effects. The contents have also been condensed onto a single board, making it slightly easier to manufacture.

The X Board was the third in the Super Scaler series of arcade hardware, and would be succeeded by the Y Board and System 32, before the Model 1 made polygonal 3D arcade games more viable and financially affordable.

Hardware

As the third in Sega's Super Scaler series of arcade hardware (after the Sega Hang-On hardware and Sega OutRun hardware), it was noteworthy for its sprite/texture manipulation capabilities, which allowed it to create high quality three-dimensional visuals, such as the scaling and rotating environments in 1987's After Burner, and the ray casting like environments in 1988's Last Survivor and 1989's Line of Fire. This trend would continue with the Y Board and the System 32, before the Model 1 made true polygonal 3D arcade games more financially affordable.

The X Board hardware was originally developed for After Burner, which began development in December 1986 and released in 1987. The first challenge when creating the hardware was sprite/texture rotation, researching how to rotate the surfaces of the sprites, which was a major milestone. Another major milestone was making the smoke trails from missiles look more realistic.[1]

Technical specifications

X Board specifications

  • Board composition: Single board
  • CPU:
  • Sound chips:
    • FM synthesis chip: Yamaha YM2151 @ 4 MHz (8 FM channels)
    • PCM sampling chip: SegaPCM (315-5218) @ 4 MHz[2] (stereo output, 16 PCM channels, 12-bit audio, 31.25 kHz sampling rate)
  • Graphics processing unit: Sega Super Scaler chipset @ 50 MHz[2]
    • Main graphics processors: 315-5197 tilemap generator, 315-5211A sprite generator, 315-5242 color encoder, 315-5275 road generator, 315-5278 sprite ROM bank control
    • Math processors: 315-5248 hardware multiplier, 315-5249 hardware divider
  • Fixed-point arithmetic capabilities: Z-buffering, depth map[3]
  • Memory: Up to 4586 KB (1180 KB main, 2940 KB video, 466 KB sound)
    • RAM: 802 KB, including 710 KB high-speed SRAM (Static RAM)[2][4]
      • Main RAM: 148 KB (52 KB work/program SRAM, 32 KB work/mirror RAM, 32 KB IC31, 32 KB IC32)
      • Video RAM: 636 KB SRAM
        • CPU: 92 KB (64 KB background tiles, 12 KB roads, 4 KB sprites, 4 KB text, 16 KB color)
        • 315-5211A: 520 KB (8 KB dual sprite banks, 512 KB dual sprite framebuffers)
        • Other: 20 KB (4 KB sprites, 4 KB roads, 12 KB text)
      • Sound RAM: 18 KB SRAM (2 KB Z80 program, 16 KB SegaPCM chip)
      • SRAM speed: 45 nanoseconds[5]
    • ROM: Up to 3784 KB (1032 KB main, 2304 KB video, 448 KB sound)
  • Video resolution: 320×224 (display), 400×262 (overscan)[4][2]
    • Scanlines: 224 (display), 262 (overscan), progressive scan
    • Framebuffer resolution: 512×256 pixels
  • Refresh rate: 59.6368 to 60 Hz (V-sync)
    • Frame rate: 59.6368 to 60 frames per second
  • Color palette: 98,304
    • 16-bit color palette: 15-bit RGB high color depth (32,768 colors) and 1-bit shadow & highlight that triples up to 98,304 colors.
  • Colors on screen: 24,576[4][2]
  • Graphical layers:
    • 4 tile planes
    • 1 text plane
    • 1 sprite plane
    • 1 road plane: Can draw 2 roads at once
    • Translucent shadows
  • Sprite plane: Dual sprite framebuffers, hardware sprite zooming, sprite/texture rotation, ray casting[4][6][2]
    • Sprite/texture sizes: 8×8 to 512×256 pixels
    • Colors per sprite/texture: 16
    • Sprites/textures on screen: 256 on screen at one time per frame, 15,267 to 15,360 scaled per second
    • Video clock cycles: 50 MHz
    • Sprite fillrate: 50 million pixels/texels per second
    • Sprite pixels/texels per frame: 833,333 (at 60 Hz) to 838,408 (at 59.6368 Hz)
    • Sprite pixels/texels per scanline: 3180 to 3200 sprite pixels/texels per scanline
    • Sprites/textures per scanline: 256

Super Monaco GP specifications

Super Monaco GP featured the following upgrades in 1989:[2]

  • Board composition: Main board + Link/Network board + Sound board + Motor board
  • CPU:
    • Main CPU: Hitachi FD1094 @ 12.5 MHz, Motorola MC68000 @ 12.5 MHz (16-bit & 32-bit instructions @ 4.375 MIPS)
    • Sound CPU: 2× Zilog Z80 @ 4 MHz (8-bit & 16-bit instructions @ 1.16 MIPS)
    • Comm CPU: Zilog Z80 @ 8 MHz (1.16 MIPS)
    • Motor CPU: Zilog Z80 @ 8 MHz (1.16 MIPS)
  • Sound chips:
    • FM synthesis chip: Yamaha YM2151 @ 4 MHz (8 FM channels)
    • PCM sampling chips: 2× SegaPCM (315-5218) @ 4 MHz (stereo output, 32 PCM channels, 12-bit audio, 31.25 kHz sampling rate)
  • Memory: Up to 5064 KB (1180 KB main, 2940 KB video, 858 KB sound, 42 KB comm/link/network, 44 KB motor)
    • RAM: 832 KB, including 720 KB high-speed SRAM (Static RAM)
      • Main RAM: 148 KB (52 KB work/program SRAM, 32 KB work/mirror RAM, 32 KB IC31, 32 KB IC32)
      • Video RAM: 636 KB SRAM
      • Sound RAM: 26 KB, including 18 KB SRAM
      • Link/Network board: 10 KB SRAM (8 KB SRAM, 2 KB Dual-Port SRAM)
      • Motor board: 12 KB
    • ROM: Up to 4232 KB (1032 KB main, 2304 KB video, 832 KB sound, 32 KB comm, 32 KB motor)
  • Sound output: 4-channel surround sound

List of games

Magazine articles

Main article: Sega X Board/Magazine articles.

References

  1. After Burner II: Developer Interviews (Yu Suzuki, Satoshi Mifune, Hiroshi “Hiro” Kawaguchi, Ryu)
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Sega X-Board Hardware (MAME)
  3. Lou's Pseudo 3D Page
  4. 4.0 4.1 4.2 4.3 Sega "X-Board" hardware notes (2004-12-03)
  5. File:HM62256B datasheet.pdf
  6. The Brief Life of Arcade First Person Shooting Games
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