Sega Y Board

From Sega Retro

YBoard topPCB.jpg
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 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

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.com/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)


Sega arcade boards
Originating in arcades









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









































PC-based hardware








05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23





























Retrieved from "https://segaretro.org/index.php?title=Sega_Y_Board&oldid=351304"