Sega Y Board

Sega Y Board
Manufacturer: Sega
Release Date RRP Code

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 equipment. Most notably, the Y Board allows for real-time rotation of sprites as well as scaling, and has a higher fillrate for the sprites/textures. Unusually, the system uses no tile layers, so graphics are rendered using only sprites/textures (a design taken by SNK for their Neo-Geo hardware in 1990).

It was succeeded by the Sega System 32 in 1990.

Technical Specifications

• Board composition: CPU Board + Video Board
• 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: Z80 @ 4 MHz (8-bit & 16-bit instructions @ 0.58 MIPS) with 2KB RAM
• Sound chips:
  • FM synthesis chip: Yamaha YM2151 @ 4 MHz (8 FM channels)
  • PCM sampling chip: SegaPCM (315-5218) @ 4 MHz (stereo output, 16 PCM channels, 12-bit audio, 31.25 kHz sampling rate)
• GPU: Sega Super Scaler chipset
  • 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 chips: 315-5248 hardware multiplier, 315-5249 hardware divider
• RAM: 812 KB, including 778 KB high-speed SRAM (Static RAM)
  • Main RAM: 208 KB (64 KB CPU 1, 16 KB CPU 2, 64 KB CPU 3, 64 KB shared)
  • Video SRAM: 598 KB (64 KB Y-sprites, 4 KB B-sprites, 512 KB sprite framebuffers, 2 KB rotation, 16 KB palette)
  • Sound RAM: 6 KB (2 KB Z80, 4 KB SegaPCM)
• Video resolution: 320×224 (display), 342×262 (overscan), progressive scan
  • Scanlines: 224 (display), 262 (overscan)
• Refresh rate: 59.6368 to 60 Hz (V-sync)
  • Frame rate: 59.6368 to 60 frames per second
• 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
• 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, dual framebuffers (based on X Board) that can be fully rotated
  • 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, dual line buffers on B-plane (512 sprite pixels/texels per line), dual framebuffers on Y-plane
  • Sprite size/resolution: 8×8 to 512×512 pixels
  • Colors per sprite/texture: 16 to 512
  • Sprites/textures per frame: 68 KB RAM for B & Y sprites allows up to 2176 sprites/textures on screen (when they are 8x8 pixels size and 16 colors each)
  • Sprites/textures per second: 129,769 (at 59.6368 Hz) to 130,560 (at 60 Hz)
  • Video clock cycles: 50 MHz
  • 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
  • Sprites/textures per scanline: 397 to 400

List of Games

• Galaxy Force (1988)
• Galaxy Force II (1988)
• Power Drift (1988)
• G-LOC Air Battle (1990)
• Rail Chase (1991)
• Strike Fighter (1991)

Gallery

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  PCB (top)

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  PCB (bottom)

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