Sega Y Board

From Sega Retro

YBoard topPCB.jpg
Sega Y Board
Manufacturer: Sega
Release Date RRP Code
Arcade
JP		 ¥? ?
Arcade
UK		 £? ?
Arcade
World		 ? ?



































The Sega Y Board is an arcade system board released by Sega in 1988 as a successor to the Sega X Board. Like the X Board before it, the Y Board was known for its 3D sprite/texture manipulation capabilities. It is the fourth in the Super Scaler series of arcade boards, after the Sega Hang-On hardware, Sega OutRun hardware and X Board.

The Y Board is quite different to the X Board in terms of design, offering a third CPU and more advanced video hardware. The Y Board allows for real-time rotation of sprites as well as scaling. It also has more memory and a higher fillrate than its predecessor, and can display significantly more sprites/textures on screen. Unusually, the system uses no tile layers (but only a single bitmap plane is used for the background), so graphics are rendered using only sprites/textures (a design taken by SNK for their Neo-Geo hardware in 1990).

The Y Board debuted with Galaxy Force in early 1988. It was succeeded by the Sega System 32 in 1990.

Technical specifications

Y Board specifications

  • Board composition: CPU Board + Video Board
  • CPU:
    • Main CPU: 3× MC68000 @ 12.5 MHz (16-bit & 32-bit instructions @ 6.563 MIPS)
      • The first 68000 ("main" in MAME) has access to the sound hardware, I/O hardware, and 64KB RAM
      • The second 68000 ("subx" in MAME) has access to the ysprites hardware, backup RAM and 16KB RAM
      • The third 68000 ("suby" in MAME) has access to the bsprites hardware, ysprites full plane rotation, bsprites palette RAM, and 64KB RAM
      • The three CPUs share 64KB of separate RAM for communication as well as the multiplier/divider hardware
    • Sound CPU: Zilog Z80 @ 4 MHz (8-bit & 16-bit instructions @ 0.58 MIPS) with 2KB RAM
  • Sound chips:
  • GPU: Sega Super Scaler chipset[1]
    • Graphics board: Sega 837-6566 Video Board @ 50 MHz (315-5196 sprite generator, 315-5213 sprite chip, 315-5242 color encoder, 315-5305 sprite generator, 2× 315-5306 video sync & rotation, 315-5312 video mixer)
    • Math processors: 315-5248 hardware multiplier, 315-5249 hardware divider
  • Fixed-point arithmetic capabilities: Z-buffering, depth map[2]
  • Memory: Up to 21.3672 MB (1232 KB main, 18.584 MB video, 1618 KB sound)
    • RAM: 824 KB, including 778 KB high-speed SRAM (Static RAM)[1][3]
      • Main RAM: 208 KB (64 KB CPU 1, 16 KB CPU 2, 64 KB CPU 3, 64 KB shared)
      • Video RAM: 598 KB SRAM (64 KB Y-sprites, 4 KB B-sprites, 512 KB dual sprite framebuffers, 2 KB rotation, 16 KB color)
      • Sound RAM: 18 KB SRAM (2 KB Z80, 16 KB SegaPCM)
    • ROM: Up to 20.5625 MB (1 MB main, 18 MB video, 1600 KB sound)[4]
  • Video resolution: 320×224 (display), 342×262 (overscan),[1] progressive scan
  • Refresh rate: 59.6368–60 Hz (V-sync)[1]
    • Maximum frame rate: 59.6368–60 FPS
  • Color palette: 2,097,152 (4096 palette banks with 512 colors each), to 16,777,216 with effects (shadow & highlight, luminosity, palette fade)
    • Colors on screen: 24,576 (unique colors), to 71,680 (320×224) with luminosity and palette fade[1]
  • Video hardware:
    • Two sprite planes with fixed Z-order
    • Lower sprite plane ("ysprites" in MAME): full scaling and rotation; also the entire plane can be rotated as a whole
      • Palettes are stored alongside the sprite table; sprite table entries hold a pointer to the palette, which itself is stored as an table of palette indirection values (?)
    • Higher sprite plane ("bsprites" in MAME): standard Sega System 16B sprite plane
  • Graphical planes: Three layers
    • B-sprite (front plane) layer: Priority on top, based on System 16B (line buffer) sprite system
    • Y-sprite (back plane) layer: Plugs into a full-screen rotation, large fillrate, double-buffered framebuffers (based on X Board) that can be fully rotated[5]
    • Sky gradient (background) layer: Bitmap plane
  • Sprite/texture capabilities: Linked list of sprites, shadow & highlight, palette fade, color rotations, different levels of luminosity, full sprite zooming & scaling on both sprite planes, full sprite framebuffer rotation on Y-sprite plane, double buffering, double-buffered line buffer on B-plane (512 pixels), double-buffered framebuffer on Y-plane[6][1][7]
    • Sprite size/resolution: 8×8 to 512×512 pixels[8]
    • Colors per sprite/texture: 16 to 512
  • Sprites/textures per frame: 2176
    • Y sprites: 2048 sprites/textures, 64 KB attribute RAM (32 KB bank per framebuffer), 16 bytes per entry[5]
    • B sprites: 256 sprites/textures, 4 KB attribute RAM, 16 bytes per entry[6]
    • Sprites/textures per second: 2176 (1 FPS) to 130,560 (60 FPS)
  • Y-plane framebuffer fillrate: 50 MPixels/s
    • Y-plane clock rate: 50 MHz
    • Maximum texels per scanline: 3200
    • Maximum sprites/textures per scanline: 400
  • B-plane line buffer fillrate: 12.5874 MPixels/s[6][9]
    • B-plane clock rate: 12.5874 MHz
    • Maximum texels per scanline: 800
    • Maximum sprites/textures per scanline: 100
  • Overall fillrate: 62.5874 MPixels/s
    • Maximum sprites/textures per scanline: 4000
    • Maximum texels per scanline: 500

Galaxy Force II specifications

Galaxy Force II featured the following upgrades in mid-1988:[1]

  • CPU:
    • Main CPU: 3× MC68000 @ 12.5 MHz (16-bit & 32-bit instructions @ 6.563 MIPS)
    • Sound CPU: Z80 @ 4 MHz (8-bit & 16-bit instructions @ 0.58 MIPS)
    • Motor CPU: Z80 @ 8 MHz (8-bit & 16-bit instructions @ 1.16 MIPS)
  • Memory: Up to 21.4 MB (1232 KB main, 18.584 MB video, 1618 KB sound, 32 KB motor)
    • RAM: 856 KB, including 778 KB high-speed SRAM (Static RAM)[1]
      • Main RAM: 208 KB
      • Video RAM: 598 KB SRAM
      • Sound RAM: 18 KB SRAM
      • Motor RAM: 32 KB
    • ROM: Up to 20.5625 MB (1 MB main, 18 MB video, 1600 KB sound)

Power Drift specifications

Power Drift featured the following upgrades in late 1988:[1]

  • Board composition: CPU Board + Video Board + Network/Link Board (16 MHz)
  • CPU:
    • Main CPU: 3× MC68000 @ 12.5 MHz (16-bit & 32-bit instructions @ 6.563 MIPS)
    • Sound CPU: Z80 @ 4 MHz (8-bit & 16-bit instructions @ 0.58 MIPS)
    • Link CPU: Z80 @ @ 8 MHz (8-bit & 16-bit instructions @ 1.16 MIPS)
  • Link MCU: Fujitsu Multi-Protocol Controller (including DMA controller and Interrupt controller)
  • Memory: Up to 21.4 MB (1232 KB main, 18.584 MB video, 1618 KB sound, 10.25 KB link)
    • RAM: 834.25 KB, including 788.25 KB high-speed SRAM (Static RAM)[1]
      • Main RAM: 208 KB
      • Video RAM: 598 KB SRAM
      • Sound RAM: 18 KB SRAM
      • Link RAM: 10.25 KB SRAM (8 KB SRAM, 2 KB Dual-Port SRAM)
    • ROM: Up to 20.5625 MB (1 MB main, 18 MB video, 1600 KB sound)

List of games

Magazine articles

Main article: Sega Y Board/Magazine articles.

Photo gallery

  • PCB (top)

  • PCB (bottom)

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 https://github.com/mamedev/mame/blob/master/src/mame/drivers/segaybd.cpp
  2. ↑ Lou's Pseudo 3D Page
  3. ↑ https://github.com/mamedev/mame/tree/master/src/mame/drivers/segaxbd.cpp
  4. ↑ http://mamedb.blu-ferret.co.uk/game/gloc
  5. ↑ 5.0 5.1 Sega "X-Board" hardware notes (2004-12-03)
  6. ↑ 6.0 6.1 6.2 Sega System 16B hardware notes (2003-01-12)
  7. ↑ Sega 16‑Bit Common Hardware, MAME
  8. ↑ Sega Y-Board Hardware (Video), MAME
  9. ↑ Sega Pre-System 16 hardware notes (2004-03-29)


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