Sega Y Board
From Sega Retro
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| Sega Y Board | |||||
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| Manufacturer: Sega | |||||
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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.
Contents
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
- Main CPU: 3× MC68000 @ 12.5 MHz (16-bit & 32-bit instructions @ 6.563 MIPS)
- 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[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]
- RAM: 824 KB, including 778 KB high-speed SRAM (Static RAM)[1][3]
- Video resolution: 320×224 (display), 342×262 (overscan),[1] progressive scan
- Scanlines: 224 (display), 262 (overscan)
- Refresh rate: 59.6368–60 Hz (V-sync)[1]
- Frame rate: 1–60 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, dual line buffers on B-plane (512 sprite pixels/texels per line), double-buffered framebuffer on Y-plane[6][1][7]
- Sprites/textures per frame: 2176
- Y-plane framebuffer fillrate: 50 MPixels/s
- Video clock rate: 50 MHz
- Maximum sprites/textures per scanline: 2048 (1–47 FPS)
- Maximum texels per scanline: 95,419 (1 FPS)
Galaxy Force II Specifications
Galaxy Force II featured the following upgrades in mid-1988:[1]
Power Drift Specifications
Power Drift featured the following upgrades in late 1988:[1]
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
PCB (top)
PCB (bottom)
References
- ↑ 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
- ↑ Lou's Pseudo 3D Page
- ↑ https://github.com/mamedev/mame/tree/master/src/mame/drivers/segaxbd.cpp
- ↑ http://mamedb.com/game/gloc
- ↑ 5.0 5.1 Sega "X-Board" hardware notes (2004-12-03)
- ↑ 6.0 6.1 Sega System 16B hardware notes (2003-01-12)
- ↑ Sega 16‑Bit Common Hardware, MAME
- ↑ Sega Y-Board Hardware (Video), MAME
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