Coin-Op Collection Presents: DECO-16 (Rohga: Armor Force / Wolf Fang: Kuhga 2001)

This morning's release for the Analogue Pocket and MiSTerFPGA platforms is the next entry on the DECO-16 platform. Rohga: Armor Force, known in Japan as Wolf Fang: Kuhga 2001, is a two player run-and-gun, built on Data East's 16-bit custom hardware.

Kuhga / Vapor Trail (1989)
Crude Buster / Two Crude (1990)
Dark Seal / Gate of Doom (1990)
The Cliffhanger: Edward Randy (1990)
Super Burger Time (1990)
Death Brade / Mutant Fighter (1991)
Tatakae Genshijin: Joe & Mac / Caveman Ninja (1991)
Robocop 2 (1991)
Thunder Zone / Desert Assault (1991)
Wolf Fang: Kuhga 2001 / Rohga (1991)
Tumble Pop (1991)
Dark Seal II / Wizard Fire (1992)
Funky Jet (1992)
Gun Ball / Nitro Ball (1992)
Diet Go Go (1992)
The Great Ragtime Show / Boogie Wings (1992)
Double Wings (1993)

Rohga puts a build-your-own war machine at its center. Before starting a run you assemble an armored suit from interchangeable arms, bodies, and legs, dozens of combinations that change how it moves and what it fires, and when the suit is wrecked the pilot bails out and fights on foot. The board behind it drives four playfields across two tilemap generators and two sprite engines merged into a single six-bit-per-pixel layer, with a HuC6280 running a YM2151 and two OKI samplers, and a DECO 104 handling protection and I/O, in a two-player cabinet.

This post covers a technical overview of Rohga on DECO-16, the work the board required, and the game itself.

Overview:

Rohga runs on Data East's DECO-16 hardware (PCB DE-0353-3), driven by a Motorola MC68000 (DECO Custom 59) at 14 MHz, with no second processor on the main bus and no encryption on its program ROM. The sound system uses a HuC6280 (DECO Custom 45) at 8.00 MHz driving a YM2151 (OPM) at 3.579 MHz and two OKI M6295 ADPCM samplers, one at 1.000 MHz and the other at 2.000 MHz. There is no YM2203 on this board, and the YM2151's CT1 and CT2 pins select the sample bank on each OKI. Audio output is mono.

The video system outputs 320x240 in a horizontal orientation at 57.445 Hz. Graphics are rendered by a set of Data East custom ICs, two DECO 55 tilemap generators drive four playfields between them, and two DECO 52 sprite engines are combined through a color mux (DECO 71 / DECO 113) into a single six-bit-per-pixel sprite layer. A DECO 104 handles the board's protection and I/O. The palette holds 2048 entries in 24-bit RGB, eight bits per channel.

Development Challenges:

The graphics are where Rohga does something the other boards from the DECO-16 platform don't. Rohga carries two DECO 52 sprite engines, and rather than drawing two separate sprite planes it runs both through a color mux, a DECO 71 paired with a DECO 113, that fuses them into one sprite layer with six bits of color per pixel instead of the usual four. That gives the armored suits and the larger enemies a wider range to draw from, sixty-four colors to a sprite rather than sixteen, and it is a large part of why the game looks richer than the rest of the platform. The core builds that layer the way the board does, reordering the sprite data as it loads so the two engines line up into a single six-bit stream, then merging them through the mux.

The core also takes its sprite timing from the real board rather than from emulation. On the PCB the sprites stay locked to the rest of the action, with no lag between them and the scene scrolling behind them. Emulators, by their own admission, do not manage this. Their sprite buffering leaves a frame of lag that the real board does not have. The core snapshots the sprite DMA list once per frame at vertical blank and draws from that snapshot, so the sprites hold in step with everything else, the way they do on the PCB, without the additional frame of lag to sync the layers.

Core Options:

The MiSTer core includes video settings for aspect ratio, vertical scaling and cropping, scandoubler effects, and H/V positioning and sync adjustments.

Audio settings provide separate OPM and two M6295 PCM toggles, each with its own volume control, covering the full sound section. Arcade dip switches are directly accessible from the OSD. Game settings include per-player auto-fire with adjustable rates, mapping options for Player 1 and Player 2, and a synced mapping mode that mirrors Player 1's layout to Player 2.

Cheats are accessible from the OSD and include per-player invincibility, infinite energy, and infinite power, along with per-player selects for the main gun, the shoulder weapon, and the melee arm, each cycling through the game's four options.

The Pocket core provides auto-fire with per-button targeting and adjustable rates. Its cheat set is a single-player subset: invincibility, infinite energy, infinite power, and the main gun, shoulder weapon, and melee arm selects. Arcade dip switches available on Pocket are Player's Vitality, Continue Mode, and Attract Mode Sound.

The core supports six sets, five Rohga: Armor Force sets and the Japanese Wolf Fang: Kuhga 2001 release.

History, Gameplay, and Regional Information:

Rohga reached arcades in 1991, developed and published by Data East, appearing in Japan as Wolf Fang: Kuhga 2001 and overseas the following year as Rohga: Armor Force. It was produced and programmed by Takaaki Inoue, with a score from Data East's in-house sound team Gamadelic, composed by Akira Takemoto under his Raika handle, and Hiroaki Yoshida, Gamadelic's founder, handling the arrange version and voice work. The game sits in the middle of Data East's loosely connected Kuhga line, between the 1989 shooter Vapor Trail and 1996's Skull Fang, though it shares little with either beyond the branding.

The game is a horizontally scrolling run-and-gun in which one or two players pilot an armored combat suit across a run of battlefields. An eight-way stick moves and aims, one button fires the main weapon, another jumps, and a third fires a heavier shoulder weapon that charges as it is held, while a melee arm swings automatically when an enemy gets close. The suit is a machine rather than a person, so it can hover and clamber up slanted walls to reach ground a foot soldier could not.

What sets Rohga apart is that you build the machine yourself. Before a mission you assemble a suit from three sets of parts, arms, bodies, and legs, four of each, sixty-four combinations in all, and the choice matters, the legs alone swap between walking, a hovering jet, four-legged footing, and tank treads, each moving and handling differently, while the arms and shoulder mounts decide how the suit fights up close and at range. The suit takes several hits before it fails, and when it does the pilot is thrown clear and fights on foot, a single hit from death, until they can climb into another machine.

The two versions are not quite the same game. The Japanese Wolf Fang is the fuller one, with between-mission story briefings, a branching mission order that leads to one of four endings, and a name shown for each of the sixty-four suits, while the overseas Rohga strips those out and runs the missions straight through to a single ending. Either way the game was well received, taking the top spot on Game Machine's table-cabinet chart in early 1992 and placing second in that year's Gamest Grand Prize, and it has aged into a genuine cult favorite, remembered as one of Data East's best action games for the freedom of its loadouts and the feel of its controls. Home versions followed in Japan, on the PlayStation in 1996 and the Saturn in 1997, both under the Wolf Fang name.

Updates:

Rohga: Armor Force is the next public release in wave 2 for Data East's DECO-16 platform. It is the game the board family takes its name from, and with it released the platform's Rohga-family boards, Nitro Ball and Wizard Fire alongside it, are all out. The two titles still ahead run on other DECO-16 hardware configurations.

The remaining wave 2 titles are:

Thunder Zone / Desert Assault (1991)
Funky Jet (1992)

We'll be shifting focus after Rohga's release. There will be an update for Boogie Wings, including a release for the Pocket, and I'll start rolling out the public release of DECO-8, as it's been in beta for over a month available in the Discord.

The public release will include games previously released and other titles coming out of beta. Here's a list of titles that will be published starting today:

Last Mission (1986)
Shackled / Breywood (1986)
Gondomania / Makyou Senshi (1987)
Garyo Retsuden (1987)
The Real Ghostbusters (1987)
Meikyuu Hunter G (1987)
Captain Silver (1987)
Psycho-Nics Oscar (1987)
Super Real Darwin (1987)
Cobra Command (1988)

The files have been pushed to GitHub, update_all, and pupdate for distribution. Please allow the updaters time to sync. Other update information shared in the previous posts can be found in their update sections at the links below:

https://www.patreon.com/posts/165187605
https://www.patreon.com/posts/165306904
https://www.patreon.com/posts/165401081
https://www.patreon.com/posts/165413183
https://www.patreon.com/posts/165417337
https://www.patreon.com/posts/165488642
https://www.patreon.com/posts/165519398

Disclaimer: All product names, trademarks, and registered trademarks mentioned are the property of their respective owners. "Analogue", "Analogue Pocket", "MiSTer", "MiSTerFPGA", "OpenFPGA", "Data East", "NEC", "Hudson Soft", "Motorola", "Yamaha", "OKI", and all derivative works are trademarks, registered trademarks, or copyrighted materials of their respective holders. Use of these names does not imply endorsement or association with this post. All rights reserved to their respective owners. This post is for educational and research purposes only.