Today's release for the Analogue Pocket and MiSTerFPGA platforms covers Captain America and The Avengers, the first entry on the DECO-32 platform. Captain America and The Avengers is a four-player beat 'em up built on Data East's 32-bit ARM-based custom chipset, the same hardware family behind:
Captain America and The Avengers (1991)Fighter's History (1993)Night Slashers (1993)Dragon Gun (1993)Locked 'n Loaded (1994)Tattoo Assassins (1994)
Captain America and The Avengers was a major commercial success for Data East, topping RePlay's upright arcade cabinet chart in the United States in November 1991 and ranking fourth on Game Machine's chart of the highest-grossing table arcade units in Japan that December.
This post covers a technical overview of Captain America and The Avengers on DECO-32, the work the board required, and the game itself.
Licensing:
Captain America and The Avengers is distributed through the Coin-Op Collection licensing portal, which serves both MiSTerFPGA and Pocket from the same dashboard.
Pocket patrons need to register their device and generate a key before launching the core. Step-by-step instructions and the FAQ are available on the Help page. More information can be found by clicking here and here.
Overview:
Captain America and The Avengers runs on Data East's DECO-32 hardware (PCB DE-0351), driven by a VLSI Technology VL86C020 ARM2 CPU at 7 MHz, repackaged by Data East as the DECO Custom 101 with encrypted instructions. The DECO-32 platform shifts the main CPU from the 68000 used across the DECO-16 family to a 32-bit ARMv2 core running in its 26-bit addressing mode, while the rest of the chipset carries over from the DECO custom-chip library that DECO-16 was built on.
The sound system uses a HuC6280 (DECO Custom 45) at 8.055 MHz pin clock running on its internal divide-by-three at 2.685 MHz, driving a YM2151 (OPM) at 3.579 MHz for FM synthesis and two OKI M6295 ADPCM samplers, one at 1.007 MHz and the other at 2.014 MHz with bank-switched sample ROM. Audio output is stereo.
The video system outputs 320x240 at 57.444 Hz. Graphics are rendered by a pair of DECO 56 tilemap generators driving the playfields, a DECO 52 sprite engine paired with a DECO 71 sprite-RAM DMA controller that double-buffers the display list it reads, and a DECO 75 protection and I/O device that also routes the four sets of player inputs the game's four-player cabinet requires. The palette holds 2048 entries in 24-bit RGB, eight bits per channel.
Development Challenges:
The DECO-32 platform's main CPU is a VLSI Technology VL86C020, an ARM2 implementation in its 26-bit addressing mode, sold by Data East as the DECO Custom 101 with the program ROM encrypted. For the core, the ARM2 is implemented as xARM2, a cycle-accurate Verilog build of the VL86C020 written new for this release, with pipeline timing taken from the VLSI VL86C020 instruction cycle tables and the register and instruction-set behavior modeled to the same reference. The decryption of the program ROM happens at the loader so the CPU runs against decrypted opcodes directly. Once DECO-32 development is complete, xARM2 will join the Coin-Op Collection Development-Modules repository on GitHub, published under CC BY-NC 4.0.
What makes Captain America and The Avengers stand out from a core-development perspective is how much of the board's actual behavior is missed or guessed at in the existing emulations of it. The same set of inaccuracies shows up in MAME, FBNeo, the commercial arcade collection that ship the game, and in a recently released FPGA core ported with AI assistance.
The MAME source carries explicit "not confirmed" annotations across the graphics and sprite paths, and the FPGA core diverges from those guesses in five concrete places, each verified against the original PCB. References below cite the MAME source because that is where the emulation was driven from, but the same behavior carries over into the other three.First off, MAME drives the screen with a 7 MHz pixel clock, an HTOTAL of 442, and a VTOTAL of 274, producing a 15.837 kHz horizontal scan rate and a 57.799 Hz refresh. The PCB runs at the same 7 MHz pixel clock but with an HTOTAL of 448 and a VTOTAL of 272, giving the standard 15.625 kHz horizontal scan rate and a 57.444 Hz refresh, which is what the core implements. The video timing also drives the DECO 52 sprite flicker effects. If the refresh rate is wrong, the flicker timing is wrong with it. This is the second game where I've found an incorrect refresh rate, but the first time I've pointed it out.
The second is the sprite RAM. The DECO 52 reads its display list out of a DMA buffer that the game writes into through a window at 0x110000, and the buffer is the full four kilobytes the chip can address. MAME draws the sprites from only the lower half of that buffer with a source-code comment that reads "only low half of sprite ram is used?" as a question, not a confirmation. The core reads the full buffer as the chip is wired to do, matching the PCB rather than the truncated MAME assumption.
The third is the backdrop color. The compositor needs to know which palette entry to fill into pixels that no layer covers, and MAME picks palette index zero with a source-code comment noting that the index is not confirmed. On hardware that backdrop is the DECO 55 playfield 3 base color, palette entry 0x400, which is what the core uses. The difference shows up at the screen edges and during transitions where layers have not yet covered the visible area.
The fourth is the DECO 55 playfield 3 tile-bank configuration. Playfield 3 on this board runs in eight bits per pixel mode, with the second DECO 55's two playfields combined into one wider color stream rather than drawn as separate layers. The bank selection in that mode is driven by control bit five feeding code bit fourteen, which the core verified from the PCB. MAME knows the playfield is running in eight bits per pixel mode but the bank-selection behavior for that mode is undocumented in the device it uses, so the rendered output is incorrect.
The fifth is sprite priority. The DECO 52 in its alternate sprite format carries priority bits in the second word of each sprite entry, and on Captain America those bits are written into the sprite list directly by the game so each sprite holds a fixed priority for its lifetime. MAME reads those bits through a path that originated in the Dragon Gun driver, with a source-code comment expressing uncertainty about whether the chip is really toggling priority per frame to fake transparency. The core does not carry that uncertainty. It reads the priority bits straight out of the sprite list as the alternate-format specification defines them, so each sprite is composited at the priority the game wrote for it without guesswork in the path. The flicker that shows up in MAME on this board is a separate problem, traceable to the wrong video timings the emulator uses, not to the priority bits themselves.
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 for all four players, mapping options for Player 1 through Player 4, and a synced mapping mode that mirrors Player 1's layout to two, three, or four players depending on the cabinet.
Cheats are accessible from the OSD and include infinite credits, a hit-anywhere helper that registers hits regardless of range, a one-hit-kills option for enemies, and per-player infinite energy and invincibility across all four players.
The Pocket core provides auto-fire with per-button targeting and adjustable rates. Its cheat set is infinite credits, infinite energy, invincibility, hit anywhere, and one-hit kills. Arcade dip switches available on Pocket are No. of Lives, Game Difficulty, Mode Select for the 4-player or 2-player cabinet, Continue Mode, Attract Mode Sound, and Stage Select.
History, Gameplay, and Regional Information:
Captain America and The Avengers was developed and published by Data East, reaching arcades in October 1991 in the West and reaching Japanese arcades that December. It was designed by Hidenobu Ito, produced by Koji Jinbo and Iwao Horita, and programmed by Tac H., Hiroshi Ōnuki, and K. Miyazawa, with a soundtrack by Tatsuya Kiuchi and Tomoyoshi Sato of Data East's in-house sound team Gamadelic. Both composers were active on the platform's other Data East boards of the period, with Kiuchi having scored Crude Buster the year before and joining Sato on RoboCop 2 earlier the same year.
The gameplay is a four-player belt-scrolling beat 'em up for one to four players at once, built around Marvel's Avengers roster. The player picks from Captain America, Iron Man, Vision, or Hawkeye, with each hero carrying their own ranged attack, the shield, the repulsor beam, energy projection, and the bow. The controls are an 8-way joystick and two buttons, attack and jump, with both buttons pressed together firing the character's signature ranged projectile as the game's Avenger Attack. There is no ammo limit on the projectile. The five stages alternate between on-foot belt-scrolling brawls and auto-scrolling shoot 'em up segments through the air, undersea, and through space.
The Marvel cameos run deep. Wasp appears as a summonable assist during the shoot 'em up segments, Quicksilver runs through the brawling stages dropping health pickups, and Wonder Man appears as well. The boss roster pulls from across the Avengers' history, with Living Laser and Klaw leading into Whirlwind on the first stage, a Sentinel mid-boss giving way to Grim Reaper on the air stage, the Wizard and a mechanical Mech Tako leading to Mandarin under the sea, Juggernaut warming up the player for Ultron in the fourth stage, and two Controllers and Crossbones standing in front of Red Skull and his mechanical Mech Skull for the space finale.
Captain America and The Avengers was a commercial success for Data East. RePlay's United States arcade trade chart placed it at number one among upright arcade cabinets in November 1991. Game Machine's January 1, 1992 issue ranked it fourth on Japan's chart of the highest-grossing table arcade units for the previous month. Sinclair User in the United Kingdom recognized it that November with a shared "Games Most Likely To Save The Universe" award alongside Sega's Spider-Man and Capcom's Captain Commando. A Data East developer interview years later credited the game with selling twenty to thirty thousand boards against a typical three to five thousand for the company's arcade releases, with overseas Europe carrying the financial weight, and described the year's bonuses at the company as all owed to Captain America.
Japan was not where those numbers came from. Marvel's comics had only a niche readership in Japan in 1991, and Japanese retro coverage of the game years later has framed it as a Marvel arcade title that arrived too early for its market, overshadowed at home by the wave of four-player belt-scrollers Capcom and Konami were running through the same arcades, including The King of Dragons, Captain Commando, and the run of Konami licensed Marvel and DC games that followed. The 1990 Cannon Films Captain America movie, which might have lent the game a tie-in push, never reached theaters and went straight to video in 1992, after the arcade game had shipped.
The core supports the seven known ROM variants of the board, the Asia revision 1.4 set MAME uses as the parent, the earlier Asia revision 1.0, the United Kingdom revision 1.4, the United States revisions 1.4, 1.6, and 1.9, and the Japan revision 0.2. All seven share the same machine configuration and game data, with the regional differences confined to the title screen text. Captain America and The Avengers shipped in two cabinet styles, a dedicated four-player cabinet with each control position locked to a character, and a two-player cabinet with free character selection.
Updates:
The DECO-32 platform will continue in chronological order from the opening list. The next entries on the way are Fighter's History, Night Slashers, Dragon Gun, Locked 'n Loaded with Wolf Fang, and Tattoo Assassins.
Tomorrow will bring a new entry to the DECO-16 platform along with a few bug fixes for the existing releases, thanks to feedback from you, the beta testers!
Disclaimer: All product names, trademarks, and registered trademarks mentioned are the property of their respective owners. "Analogue", "Analogue Pocket", "MiSTer", "MiSTerFPGA", "OpenFPGA", "Data East", "VLSI Technology", "ARM", "NEC", "Hudson Soft", "Motorola", "Yamaha", "OKI", "Marvel", "Captain America", "The Avengers", "Cannon Films", "Sega", "Capcom", "Konami", 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.