Frequently Asked Questions¶
General¶
What is 5DO?¶
5DO is a source-available C#/.NET 10 emulator for the Panasonic 3DO Interactive Multiplayer. It includes an Avalonia desktop app, a headless CLI, a deterministic save-state and TAS format, and a test/differential harness.
Is 5DO a fork of 4DO or FreeDO?¶
5DO is a C# port derived from the FreeDO 3DO emulation core. 4DO and Opera/libopera are forks of FreeDO; their source and behavior are used as references. 5DO is not a drop-in replacement for 4DO and does not load 4DO .state files.
Is 5DO "open source"?¶
The source is publicly available, but the license is the FreeDO modified GNU LGPL, which is not a standard OSI license and includes additional restrictions. 5DO is donationware: non-commercial, source-available, and funded by voluntary donations. Read Licensing and the project license.
Why is it called 5DO?¶
The project name is a play on 3DO. C# identifiers cannot start with a digit, so the solution and namespace prefix use FiveDo.
Getting started¶
Does 5DO include a BIOS or games?¶
No. You must supply a legally obtained 3DO BIOS and legally obtained disc images. The repository never includes BIOS ROMs, game images, or extracted game assets.
Where do I get a BIOS?¶
Dump it from a 3DO console you own, or obtain it through a lawful source in your jurisdiction. Do not ask for or share copyrighted BIOS files in issues, discussions, or pull requests.
Which disc formats are supported?¶
- ISO (2048-byte sectors)
- BIN (2352-byte sectors)
- CUE+BIN, including multi-track and CD-DA layouts
- CHD, including parent/child images
- M3U/M3U8 playlists for multi-disc games
How do I open a game from a launcher?¶
A positional disc path or --disc <path> opens and auto-starts the game. See Installation and the User guide.
Is there a download?¶
Yes - v1.1.0 is available on GitHub Releases. There is one bundle per system (Windows x64, Linux x64, macOS x64), and each bundle contains both the desktop app and the CLI. Install the .NET 10 Runtime first; the bundles do not include it. You can also build from source.
Compatibility¶
How compatible is 5DO?¶
The full-collection loadability sweep covered 594 disc images: 593 render, 1 known boot failure (Crash 'n Burn Japan), and 0 not-loadable rows. The 12-title compatibility matrix and known issues are the supported v1.0 set; full visual review and high-resolution CEL research are post-1.0. This is a documented-compatibility project, not a claim of full 3DO library compatibility.
See Compatibility, Game compatibility list, and Known issues.
Why does a game show a black screen?¶
The first frame can be black while the game loads its own OS or initializes video. Some titles need a different BIOS or more than 3,000 frames. Try:
dotnet run --project src/FiveDo.Cli -- run game.chd --bios-auto bios --frames 12000 `
--frame-out last.png
Check the compatibility results and Troubleshooting before filing a report.
Does 5DO support PAL games?¶
Yes. NTSC, PAL1 (320×288@50), and PAL2 (384×288@50) modes are implemented, with automatic region selection, per-game overrides, and 50 Hz audio pacing. PAL support is still being validated across the library.
Does 5DO support 4K?¶
5DO renders CELs natively at 320×240 (and an opt-in 640×480 high-resolution mode). 4K is output upscaling, not internal 4K CEL rendering. The OpenGL/Vulkan presenters can output 4K with nearest, sharp-bilinear, CRT, xBR, FSR, and HQx filters.
Is there netplay or achievements?¶
No. Netplay, achievements, a full debugger UI, installers, and a guest CPU JIT are post-1.0 or explicitly out of scope for v1.
Saves, cheats, and TAS¶
Are save states compatible with 4DO?¶
No. 5DO uses a native .tdos format. Format v3 is current; v1 and v2 states remain readable. State compatibility across 5DO builds is documented in Save states.
Can I rewind or fast-forward?¶
Yes. Rewind is on by default with a compressed 30–300 second window. Press R to rewind one second or Shift+F9 to step back one frame. Hold Tab to fast-forward at 2×–10×; audio is muted while fast-forwarding.
Where are saves, screenshots, and logs?¶
Under the 5DO data directory shown in Settings > Paths or About, unless portable mode is active. Typical Windows location:
See Configuration for the full layout.
Can I record a speedrun or TAS?¶
Yes. 5DO records deterministic .5domovie files with per-frame PBUS packets, an optional starting state, replay/verify/branch commands, and a desktop movie editor. See TAS movies.
Does 5DO support cheats?¶
Yes. Per-game raw/typed/conditional/button codes are supported in the desktop manager and the cheat CLI. See Cheats.
Platforms and performance¶
Does 5DO run on Linux and macOS?¶
Builds are published for Windows, Linux, and macOS on x64 as framework-dependent bundles; users install the .NET 10 runtime. Windows x64 is the validated target. Linux and macOS runtime validation is ongoing; please report issues with a diagnostics bundle.
What are the performance targets?¶
The core targets 60 fps at 4K output with presentation-only scaling. On the reference machine, Road Rash's 3D race measures 4.20 ms/frame total (p99 7.40 ms), and 4K sharp-bilinear measures GPU p99 0.089 ms / present p99 0.208 ms on an RTX 4070. See Performance.
Do I need a discrete GPU?¶
No. OpenGL 3.3 or GLES 3.0/3.1 is used when available, with a CPU fallback. CRT, xBR, FSR, and HQx filters are opt-in and may need faster hardware.
Does 5DO collect telemetry?¶
No. The app does not send telemetry. Diagnostics bundles are created locally and scrub user paths and account names before you choose to attach one to a report. See Privacy.
Contributing and support¶
How do I report a bug?¶
Use the bug report issue form. Include:
- 5DO version, OS, architecture, renderer, and audio backend;
- the exact command line or UI steps;
- BIOS MD5 and disc format (never upload the files);
- expected and actual behavior;
- a privacy-scrubbed diagnostics bundle and, if possible, a minimal input script or movie.
How do I contribute?¶
Read Contributing, the Developer guide, and Build and test. Start small: documentation fixes, test cases, and reproducible compatibility reports are all valuable.
Where can I ask questions?¶
Use GitHub Discussions for questions and ideas. Use issues for reproducible bugs and concrete feature requests. Report security problems privately through the security policy.
Why was my issue closed?¶
Compatibility reports without a version, BIOS/disc details, or reproduction steps are hard to act on. A maintainer may close an issue that duplicates a documented known issue or that cannot be reproduced. The templates and Troubleshooting page list the required evidence.