VCO Object

VCO Object
Manufacturer: Sega
Release Date RRP Code World 1981-10 ? ?

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.

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.

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

Technical specifications

VCO Object specifications

• Board composition: CPU Board, Sound Board, P-ROM Board
• CPU: Zilog Z80 @ 5 MHz (8/16-bit instructions, 0.725 MIPS)
• Sound board: Sega Sound Board

• Sound chip: Custom
• Audio output: Stereo

• PPI: 4x Intel 8255

Graphics

• Graphics chipset:

• 315-0138: Custom Chip PA-06R (PAL16R4MJ)
• 315-0139: Custom Chip PA-06L (PAL16L8MJ)
• 12x 314-0101: 74LS283 4-bit Binary Full Adder with Fast Carry
• Video scaling hardware: 8x Voltage Controlled Oscillators (VCOs)

• Video clock rate: 9.984 MHz

• Pixel clock rate: 4.992 MHz

• Video resolution:

• Horizontal: 256×224 (display), 320×264 (overscan)
• Vertical: 224×256 (display), 264×320 (overscan)

• Analog scaling resolution:

• Horizontal: 512×224 (display), 640×264 (overscan)
• Vertical: 224×512 (display), 264×640 (overscan)

• Refresh rate: 59.090909 Hz (V-sync)

• Frame rate: 59.090909 frames per second

• Color palette: 832

• Colors on screen: 256

• Background planes:

• Tilemap layer: 8×8 pixel tiles, 4 colors per tile, scrolling, tile flipping
• Bitmap layer

• Sprite capabilities: Pseudo-3D sprite-scaling (analog scaling), line buffer, 64 sprites on screen, 16 sprites per scanline, 4 to 8 colors per sprite

• Sprite sizes: 8×8 to 256×224 texels
• Sprites on screen: 128 sprites (8 KB sprite position RAM, 8 bytes per sprite position)
• Fillrate: 4.992 MPixels/s
• Sprites per scanline: 16 sprites, 322 texels

Memory

• RAM: 12 KB

• 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

• Main ROM: 24 KB main
• VROM: 129.875 KB
• Sound ROM: 32 bytes

• Bandwidth:

• RAM: 5 MB/s (Fujitsu SRAM, 8-bit, 3.333333 MHz, 200 ns)
• Main ROM: 5 MB/s (EPROM, 8-bit, 5 MHz, 200 ns)
• VROM: 2.222222 MB/s (EPROM, 8-bit, 2.222222 MHz, 450 ns)

SubRoc-3D specifications

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

• Frame rate: 30 frames per second
• Color palette: 768
• Stereoscopic 3D: Sega-Matsushita active shutter 3D system
• RAM: 14.75 KB

• Main RAM: 6.25 KB (2 KB main, 2 KB analog reset, 256 bytes input, 2 KB handle)
• VRAM: 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)

• ROM: 302.5 KB

• Main ROM: 40 KB
• VROM: 262.5 KB (256 KB sprites, 4 KB foreground tiles, 768 bytes color, 1.75 KB other)

Zoom specifications

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

• 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

• Frame rate: 60 frames per second
• Color palette: 1536

• Colors on screen: 1024

• RAM: 104 KB (SRAM)

• Main RAM: 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)
• VRAM: 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)

• ROM: 310.5625 KB

• Main ROM: 40 KB
• VROM: 270.5625 KB (256 KB sprites, 4 KB foreground tiles, 9.5 KB color, 1.0625 KB other)

List of games

Only a small handful of games make use of VCO Object hardware:

• Turbo (1981)
• SubRoc-3D (1982)
• Buck Rogers: Planet of Zoom (1982)
• Zoom 909 (1982)

References

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