VCO Object

From Sega Retro

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VCO Object
Manufacturer: Sega
Release Date RRP Code

VCO Object arcade hardware was used by Sega for a brief period between 1981 and 1983. It was Sega's second attempt at creating hardware specifically designed for sprite scaling (after the Sega Fonz hardware in 1976), something that would be widely used in the Super Scaler series of arcade hardware (Sega Hang-On, Sega OutRun, X Board, Y Board, System 32), and a handful of Sega System boards in between.

The hardware debuted with the release of Turbo, and is also known as the Turbo Hardware because of this. It is also known as the Sega Z80-3D system.[1]

All VCO Object games rely on external LED displays for parts of the HUD. This means extra precautions must be taken when attempting to emulate VCO Object games.

Hardware

It was the first system specifically designed for pseudo-3D sprite-scaling graphics, using an analog scaling technique, with Voltage Controlled Oscillators (VCOs) generating clock signals controlling the data fetched from the sprite/object ROM; the slower the clock signal, the larger the sprite on screen.[2]

In 1982, SubRoc-3D also introduced an active shutter 3D system, jointly developed by Sega with Matsushita (now Panasonic).[3]

Technical Specifications

VCO Object

Graphics

  • Graphics chipset:[6]
    • 315-0138: Custom Chip PA-06R (PAL16R4MJ)
    • 315-0139: Custom Chip PA-06L (PAL16L8MJ)
    • Video scaling hardware: 8× Voltage Controlled Oscillators (VCOs)[2]
  • Video clock rate: 9.984 MHz[7]
    • Pixel clock rate: 4.992 MHz[5]
  • Video resolution:[5]
    • Horizontal: 256×224 (display), 320×264 (overscan)
    • Vertical: 224×256 (display), 264×320 (overscan)
  • Analog scaling resolution:[8]
    • Horizontal: 512×224 (display), 640×264 (overscan)
    • Vertical: 224×512 (display), 264×640 (overscan)
  • Refresh rate: 59.090909 Hz (V-sync)[5]
  • Color palette: 832[5]
  • Background planes:
  • Sprite capabilities: Pseudo-3D sprite-scaling (analog scaling), line buffer, 64 sprites on screen, 16 sprites per scanline, 4 to 8 colors per sprite[9][5]
    • Sprite sizes: 8×8 to 16×16 texels
    • Sprites on screen: 128 sprites (8 KB sprite position RAM, 8 bytes per sprite position)
    • Fillrate: 4.992 MPixels/s, 84,480 pixels per frame
    • Sprites per scanline: 16 sprites, 322 texels

Memory

  • RAM: 12 KB[5]
    • Main RAM: 4.25 KB (2 KB main, 2 KB analog reset, 256 bytes input)
    • VRAM: 7.75 KB (2 KB video, 256 bytes sprite line buffer, 1 KB sprite position, 2 KB characters, 512 bytes collision, 2 KB collision clear)
  • ROM: 153.90625 KB[5][10]
    • Main ROM: 24 KB main
    • VROM: 129.875 KB
    • Sound ROM: 32 bytes
  • Bandwidth:[11][6]

SubRoc-3D

SubRoc-3D featured the following hardware changes and upgrades in mid-1982:[5]

  • RAM: 14.75 KB
    • Main: 6.25 KB (2 KB main, 2 KB analog reset, 256 bytes input, 2 KB handle)
    • Video: 8.5 KB (2 KB video, 1 KB sprite line buffer, 1 KB sprite position, 2 KB characters, 512 bytes collision, 2 KB collision clear)
  • Frame rate: 30 frames per second
  • Color palette: 768
  • Stereoscopic 3D: Sega-Matsushita active shutter 3D system

Zoom

Zoom 909 and Buck Rogers: Planet of Zoom featured the following hardware upgrades in late 1982:[5]

  • Board composition: CPU board, Sound board, ROM board
  • CPU: 2x Z80 @ 5 MHz (1.45 MIPS)
    • Zilog Z80 @ 5 MHz
    • Sega 315-5014 (Z80) @ 5 MHz
  • RAM: 104 KB (96 KB DRAM, 8 KB high-speed SRAM)
    • Main: 39.5 KB (2 KB main, 2 KB analog reset, 256 bytes input, 2 KB handle, 2 KB CPU 2 mirror, 31.25 KB other)
    • Video: 64.5 KB (2 KB video, 1 KB sprite line buffer, 1 KB sprite position, 2 KB characters, 512 bytes collision, 2 KB collision clear, 56 KB bitmap)
  • Frame rate: 60 frames per second
  • Color palette: 1536
    • Colors on screen: 1024

List of VCO Object Games

Only three games make use of VCO Object hardware:

References

  1. ↑ https://github.com/mamedev/mame/blob/master/src/mame/video/turbo.cpp
  2. ↑ 2.0 2.1 Sega VCO Object Hardware (System 16)
  3. ↑ Subroc-3D, The Arcade Flyer Museum
  4. ↑ File:Turbo Schematics.pdf
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 Sega Z80-3D system (MAME)
  6. ↑ 6.0 6.1 Turbo: Operating Instructions and Service Manual (page 106)
  7. ↑ [https://github.com/mamedev/mame/blob/master/src/mame/includes/turbo.h Sega Z80-3D system (data) (MAME)
  8. ↑ https://github.com/mamedev/mame/blob/master/src/mame/includes/turbo.h
  9. ↑ 9.0 9.1 Sega Z80-3D system (video hardware) (MAME)
  10. ↑ Turbo (MAME)
  11. ↑ File:Turbo Schematics.pdf, page 19
  12. ↑ MB8128 Datasheet
  13. ↑ NTE2764 Datasheet


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