Jotego's new MiSTer update fixes Konami CPUs and adds Wardner

FPGA developer Jose Tejada has released a major update to his Konami arcade cores. He probed a physical Vendetta circuit board to measure the original CPU's behavior. The update revises the JTKCPU module used by games like The Simpsons and Aliens, and arrives alongside a brand new core for Toaplan's 1987 platformer Wardner.

Tejada, who publishes under the name Jotego, used Wickerwaka's PicoROM tool to run instruction probes directly on a real Konami 053248 chip. This research exposed undocumented instruction encodings and several instances where the previous FPGA model set condition flags incorrectly. Arcade games often rely on these exact flags to make logic decisions. A tiny CPU inaccuracy can cause visible glitches or incorrect behavior on screen.

Konami's arcade boards from the late 1980s and early 1990s are a massive engineering challenge. The company relied heavily on custom proprietary microprocessors and graphics chips. Accurately modeling this custom silicon is essential for bringing full libraries of Konami arcade classics into the open-source FPGA ecosystem. This physical hardware verification is a huge step forward.

The flag fixes apply to Crime Fighters, Gang Busters, Super Contra, Thunder Cross, Ajax, Haunted Castle, Parodius DA!, Surprise Attack, and Vendetta. I'm curious to see how much of a difference this actually makes in gameplay. We need more testing. Tejada noted that players should revisit their favorites to find exactly where the changes surface. He's also updating his fork of the ASL assembler tool and the MAME software emulator with the new findings.

Toaplan's fantasy platformer needs the big board

The other major addition is Wardner, known in Japan as Wardner no Mori and in some regions as Pyros. It's a 1987 fantasy action game from Toaplan that gives you a fireball attack, a jump, and a lot of moving platforms. Marc Emmerson brought the core to the project, utilizing a TMS320C10 DSP core developed by IkaMusume.

The hardware uses multiple Z80 processors. It's a heavy enough configuration that it won't fit on the smaller SiDi FPGA devices. You'll need a standard MiSTer setup or an Analogue Pocket to run it.

Beta keys and bug fixes

You'll need a new beta key to run these latest test builds. The key file changed with this release, so MiSTer users need to replace their jtbeta.zip file, and Analogue Pocket users must update beta.bin. If you skip this step, the beta cores will just sit at their credits screens.

The patch notes on Patreon list several other welcome corrections. Pac-Land gets its CUS30 noise channels back for water spout sound effects, and the lantern effect in later rounds is fixed. Teenage Mutant Ninja Turtles 2 no longer misplaces enlarged and shrunken sprites. Thunder Cross has corrected hit detection for the boss flames.

Jotego also implemented video RAM changes for the CPS1, CPS1.5, and CPS2 cores to prevent slowdowns when a game fills the memory rapidly. Finally, BlockOut and Volfied have graduated from beta status into public releases.