Neo-Geo MVS

The Neo-Geo MVS was an cartridge based arcade system board produced by SNK.

Details

The Neo-Geo MVS is a cart based arcade board. The individual games are held on a cart roughly 1.5x the size of a vhs tape. Commonly setup in configurations of 2 or 4 slot boards, it was a big draw to arcade owners because more games could be fit into less floor space.

The slot 1 boards are Jamma compatible, while 2/4/6 slot boards use MVS standard, which is very close to Jamma but requires an adapter to work in Jamma cabinet or you risk damaging the motherboard audio.

Hardware

Main processor: Motorola 68000, often produced by another manufacturer, running at 12 MHz Co-processor: Zilog Z80 running at 4 MHz. This is also used as an audio controller.

Memory

Main memory (used directly by 68000): 64 KB Main video memory : 84 KB Video memory: 64 KB (32 KB x2) Palette memory : 16 KB (8 KB x 2) Fast video RAM : 4 KB (2 KB x 2) Sound memory (used directly by Z80): 2 KB

Display

Display resolution: 320×224 (many games only used the centermost 304 pixels) Color palette: 65,536 (16-bit) (Not RGB565, but RGB666, where the lowest bit of each channel is shared with one bit[10]) Maximum colors on screen: 4,096 (12-bit) Maximum sprites on screen: 380 Minimum sprite size: 1×2 Maximum sprite size: 16×512 Maximum sprites per scanline: 96 Background layers: 0 Aspect ratio: 4:3 A/V output: RF, composite video/RCA audio, RGB (with separate 21 pin RGB cable FCG-9).

Sound

Sound chip: Yamaha YM2610 4 FM channels, 4 operators per channel 3 SSG channels 1 Noise channel 7 ADPCM channels Work RAM (sound): 2KB Sound ROM 128KB on-board (only less than 32KB used) up to 512KB sound ROM on cartridges

Software

Programming / Hacking details.

Mods

Battery

One of the first things you should do after receiving a MVS motherboard is check for battery leakage and replace the stock battery with something more usable. The type of battery used is getting harder to find in comparison to the alternative.

Luckily most of these boards can easily take a coin cell battery holder and use cr2032's to hold high scores.

After removing the stock battery, which is just a simple 2 point de-soldering job. You will want to remove the resistor which closes the charging circuit, as cr-2032's are not rechargeable. Near the location of the old battery, and your new coin cell holder, there will be a 470 ohm resistor (needs verification, don't remember if its 470ohm or 1k), this should be removed.

I would recommend soldering in the coin holder so that the new battery is on the bottom of the motherboard, this makes it easy to replace. On some 1 slots and all 2-6 slots you would need to remove the case and secondary board if you do it the other way.

Once the new battery is in place you should be able to boot the system, rack up a high score, and have it save through a power off.

Useful Links

Neo-Geo.com Long running site, great forums for finding technical help and good deals on anything Neo-Geo.

HardMVS Cabinet pictures, motherboard manuals.