🕹️ ZN-1 Capcom + ZN-2 Capcom for MiSTer

Two core releases. One post. Downloads below.

• Yes audio mixing quality will be improved.

• Yes SFEX2P is playable but with problems.

ZN1-Capcom and ZN2-Capcom together — FPGA implementations of the Capcom variants of Sony's first- and second-generation PlayStation-derived ZN arcade platforms.

Both generations share the same architectural lineage, and Capcom paired them with its distinctive QSound hardware. They also share many of the engineering challenges we had to solve along the way, so releasing them together felt like the right way to tell the story.

Two boards, one family.

Sony's ZN hardware took technology closely related to the original PlayStation and adapted it into a modular arcade platform.

At the heart of both generations is a PlayStation-derived MIPS CPU/GPU/SPU architecture, surrounded by hardware that distinguishes the ZN boards from a retail PlayStation:

• A publisher-specific arcade BIOS — coh1002c for the 2 MB VRAM Capcom ZN-1 configuration and coh3002c for Capcom ZN-2

• Banked mask-ROM game storage instead of the PlayStation's CD-ROM subsystem

• CAT702 challenge/response security devices, including separate protection for the BIOS and game

• JAMMA arcade I/O for coin, service, controls, and Capcom's additional six-button fighter inputs

• Battery-independent EEPROM/NVRAM storage for configuration and bookkeeping

• The Capcom QSound subsystem: an 8 MHz Z80 paired with the DL-1425/DSP16A-based QSound processor and external sample ROMs

Where ZN-2 goes further

ZN-2 wasn't simply a renamed ZN-1.

Sony upgraded the CPU subsystem substantially, using the CXD8661R in place of ZN-1's CXD8530CQ, while retaining the PlayStation architectural foundation. ZN-2 also standardized 2 MB of VRAM and provided 4 MB of main RAM, giving developers considerably more room for more demanding games.

Those improvements helped make games such as Street Fighter EX2, Rival Schools, Plasma Sword, Tech Romancer, and Strider 2 possible on the platform.

🎮 What plays

ZN-1 Capcom — 5 titles

• Street Fighter EX

• Street Fighter EX Plus

• Star Gladiator: Episode I – Final Crusade

• Battle Arena Toshinden 2

• Gallop Racer

The first four use Capcom's QSound subsystem.

Gallop Racer is the exception: although its game board is based on the Capcom QSound design, its QSound program/sample ROM positions are unpopulated and the game relies on the PlayStation audio hardware instead.

All five titles boot and play on the core.

ZN-2 Capcom — 7 distinct titles

• Rival Schools: United By Fate / Shiritsu Justice Gakuen

• Street Fighter EX2

• Plasma Sword: Nightmare of Bilstein / Star Gladiator 2

• Tetris: The Grand Master

• Tech Romancer / Choukou Senki Kikaioh

• Street Fighter EX2 Plus - Known Performance Issues

  • Known A/V + CPU problems.

• Strider 2 / Strider Hiryu 2

The supported regional and revision sets are handled through their corresponding MAME ROM definitions, and merged MAME romsets are supported by both cores.

✨ Shared features

• DB9 / DB15 / Saturn controller support through the MiSTer USER port and compatible Antonio Villena-style DB9/SNAC8 splitter hardware

• Mega Drive 3/6-button pads through DB9 MD mode

• Neo Geo-style DB15 arcade sticks

• 1P/2P selection through the UserIO Joystick OSD option

• PSX SNAC controller support while USB controllers continue to operate normally

• CRT Adjust with analog H-Size, H-Position, and V-Shift controls

• 90° TATE rotation, clockwise or counter-clockwise

• 480i deinterlacing and HDMI synchronization options

• A custom pause screen with scrolling credits recognizing the MiSTer preservation community

🚧 What's ahead

We're proud of where both cores are today, while there are still a few things we want to improve.

Native ZN-2 CPU timing

The original ZN-2 hardware provided substantially more CPU performance than ZN-1.

The current FPGA implementation still uses a timing compromise: rather than running the CPU domain exactly as the original ZN-2 hardware did, it combines the existing CPU clocking with reduced memory wait-state overhead to achieve the required game pacing.

For normal gameplay this works remarkably well, but the heaviest Street Fighter EX2 Plus scenes can still expose the difference.

The next major milestone is therefore a true ZN-2 CPU-domain implementation at the original board timing.

The goal is:

Authentic hardware timing by default.

The current faster pacing behavior can then remain available as an optional Turbo mode.

One small ZN-2 audio issue

Street Fighter EX2 Plus currently has a brief cosmetic audio artifact near the end of its intro sequence, immediately after the spoken voice line.

It doesn't affect gameplay, but it's on the list.

Completing the wider ZN-1 family

Capcom was only one part of the ZN-1 ecosystem.

Other publishers paired Sony's ZN-1 main board with their own game boards and audio hardware.

Our existing sibling implementations already cover additional Taito and Tecmo/Video System configurations.

Still on the roadmap are implementations for the remaining sound-board families, including Raizing's YMF271-based hardware, Atlus's YMZ280B configuration, and eventually the Acclaim ADSP-2181-based hardware.

Each one brings another piece of the wider ZN-1 ecosystem into the MiSTer project.

Standing on shoulders: JTDSP16 and the community

Every QSound note produced by these cores ultimately runs through jtdsp16, Jose Tejada (Jotego)'s GPL implementation of the DSP16A architecture used by Capcom's DL-1425 QSound hardware.

Originally developed for Jotego's CPS1.5/CPS2 work, the processor implementation is used here largely intact.

Our work was primarily in adapting everything around it to the very different environment of a PlayStation-derived ZN arcade board:

• Runtime DSP-program loading

• A latency-tolerant sample-ROM interface for MiSTer's shared SDRAM

• The sample-fetch corrections that eliminated the transient-address corruption

• A serial audio receiver that reconstructs the DSP output

• Clock-enable generation appropriate to our FPGA clock domain

And one point deserves to be stated clearly:

The QSound bugs we encountered were in our integration around JTDSP16 — not in Jotego's processor implementation.

Thank you, Jotego.

These cores also stand on the work of:

PSX_MiSTer by Robert Peip (FPGAzumSpass) — providing the PlayStation CPU, GPU, GTE, DMA, MDEC, SPU, memory, and broader architectural foundation.

The MiSTer framework by Alexey Melnikov (Sorgelig) and its many contributors.

The T80 Z80 core by Daniel Wallner and contributors.

MiSTer-CRT-Adjust.

The MiSTer DB9/DB15/Saturn ecosystem, including Antonio Villena's splitter hardware, control modules by Aitor Pelaez (NeuroRulez), work by Victor Trucco and Fernando Mosquera, and the Saturn protocol adaptation by Timothy Redaelli through the MiSTer-DB9-Pro framework.

The ZN-specific board support and original chip-level reimplementations in these cores are by XelaNotPu.

MAME has been an invaluable behavioral and hardware reference throughout development. No MAME source code is incorporated into these cores.

Thank you to everyone supporting this preservation work.

Much more soon.

Legal Disclaimer

No Affiliation.
These cores are unofficial, independent projects and are not affiliated with, endorsed by, or sponsored by Sony Interactive Entertainment, Capcom, Arika, Takara/Takara Tomy, QSound Labs, or any other applicable rights holder.

Trademarks.
PlayStation, ZN-1, ZN-2, QSound, Capcom, Street Fighter, Star Gladiator, Rival Schools, Plasma Sword, Strider, Tech Romancer, Battle Arena Toshinden, Gallop Racer, Tetris, and all other product names, game titles, characters, logos, and trademarks referenced here remain the property of their respective owners.

Sega, Mega Drive, Saturn, and Neo Geo names are referenced solely to describe compatibility with corresponding controller standards or hardware.

All names are used descriptively to identify the hardware, software, and interfaces being discussed.

No ROMs or Manufacturer Firmware.
These core releases do not distribute game ROMs, manufacturer BIOS images, QSound DSP program data, or other proprietary manufacturer firmware.

Required external data — including applicable ZN BIOS/game ROM data and the DL-1425 DSP program — is loaded separately at runtime and is not embedded in the FPGA bitstream.

MRA definitions identify compatible ROM sets but do not contain the game ROM data themselves.

Users are responsible for obtaining and using any required external data in accordance with the laws applicable in their jurisdiction.

Security-Chip Reimplementation.
Original ZN hardware uses CAT702 challenge/response security devices. These cores independently reproduce the hardware behaviour required for compatibility and preservation.

Laws governing technological protection measures, including provisions such as U.S. DMCA §1201, vary by jurisdiction and circumstance. Nothing in this release should be interpreted as legal advice, and users remain responsible for compliance with applicable law.

Purpose and Reference Material.
These are independent hardware-preservation and interoperability projects.

The FPGA implementation was developed from hardware observation, testing, publicly available documentation, existing open-source components, and behavioral references including MAME.

No proprietary source code from Sony, Capcom, or other original manufacturers is included, and no MAME source code is incorporated into the project.

Open-Source Licensing.
The combined FPGA project is distributed under the applicable GNU GPL terms described by the source repository. Individual upstream components retain the licenses and copyright notices specified by their respective authors.

Refer to the source tree and accompanying license files for the authoritative licensing terms for each component.

User Responsibility.
Users are responsible for ensuring that their use of these cores and any externally supplied ROM, BIOS, firmware, or other data complies with applicable copyright and other laws in their jurisdiction.

No Warranty.
The software and FPGA implementations are provided "AS IS", without warranty of any kind, express or implied, to the extent permitted by applicable law.

This is a preservation and compatibility project, not an official commercial hardware product.

Source: Github