Deecy

Free plan LinuxWindows

What Deecy is

Deecy is an experimental, open-source Dreamcast emulator for Windows and Linux, written in Zig. It can load .gdi, .cdi, and .chd disc files through its command-line interface. Setup requires Dreamcast BIOS and flash dumps named dc_boot.bin and dc_flash.bin in the data folder; users then select the directory containing their disc images. Deecy should detect and map controllers automatically, with manual guest-port assignment and customizable keyboard bindings also available. Keyboard shortcuts provide four save-state slots and four matching load-state slots. The emulator supports fullscreen mode and unlimited emulation speed. On Linux, the --scif option pipes a serial port to /tmp/deecy/scif for dcload-serial prototyping. DreamPicoPort is available as an optional build dependency. The project offers unstable builds and maintains a compatibility list. It is free, though several areas remain unfinished, including AICA filtering, framebuffer handling, exclusion modifier volumes, and renderer features.

Who it suits

Deecy may suit Dreamcast users on Windows or Linux who can provide the required BIOS and flash dumps. Its Linux serial option may also interest people prototyping with dcload-serial.

What it does well

Loads .gdi, .cdi, and .chd disc files.
Offers four save-state and four load-state slots.
Supports automatic controller mapping and configurable keyboard bindings.
Available for Windows and Linux at no cost.

What to know first

Requires BIOS and flash dumps.
Described as experimental, with unfinished areas.
The available builds are unstable.

Limits

Deecy requires BIOS and flash dumps named dc_boot.bin and dc_flash.bin. The project describes its builds as unstable and lists unfinished areas including AICA filtering, framebuffer handling, exclusion modifier volumes, and renderer features.

Getting started

Visit the Deecy project website and download the build for Windows or Linux.
Decompress the downloaded archive.
Place dc_boot.bin and dc_flash.bin in the data folder.
Select the folder containing your Dreamcast disc images.
Load a .gdi, .cdi, or .chd file through the command-line interface.

Verdict

Deecy provides core Dreamcast emulation features across Windows and Linux, including several disc formats, controller options, and save-state slots. Its experimental status, unstable builds, and required BIOS files are important considerations.

Questions

Is Deecy free?

Yes. The project offers Deecy as a free, open-source emulator.

Which operating systems does Deecy support?

It supports Windows and Linux, with unstable builds provided for both.

Does Deecy require Dreamcast BIOS files?

Yes. Setup requires BIOS and flash dumps named dc_boot.bin and dc_flash.bin in the data folder.

Which disc formats can Deecy load?

Its command-line interface can load .gdi, .cdi, and .chd files.

What license does Deecy use?

The rest of Deecy is MIT licensed. MAME data uses BSD-3-Clause, and CHD features are based on MAME code.

How do I report a bug?

The project directs bug reports to its GitHub issue tracker, but issue creation in the repository is restricted.

Facts from Deecy's own pages

BIOS requirement: Installation requires copying BIOS and flash dumps named dc_boot.bin and dc_flash.bin into the data folder. · senryoku.github.io, 1 Oct 2026
Compatibility: The project maintains a compatibility list and accepts contributions to its dedicated compatibility repository. · senryoku.github.io, 1 Oct 2026
Controller support: Deecy should automatically detect, map and use controllers, with manual assignment to guest controller ports available in Settings. · raw.githubusercontent.com, 1 Oct 2026
Disc formats: The command line interface can load and execute .gdi, .cdi and .chd disc files. · raw.githubusercontent.com, 1 Oct 2026
Disc images: Users select the folder where their Dreamcast disc images are stored. · senryoku.github.io, 1 Oct 2026
Downloads: The official site provides unstable builds for Windows and Linux. · senryoku.github.io, 1 Oct 2026
DreamPicoPort: DreamPicoPort support is available and can be disabled with the -Ddreampicoport=false build option. · raw.githubusercontent.com, 1 Oct 2026
DreamPicoPort integration: DreamPicoPort support is available as an optional build dependency and can be disabled with -Ddreampicoport=false. · github.com, 30 Sept 2026
fullscreen and speed: The emulator supports fullscreen toggling and an unlimited emulation-speed mode. · github.com, 30 Sept 2026
funding: The official site asks supporters to make a one-time donation through GitHub Sponsors. · senryoku.github.io, 30 Sept 2026
installation: Users download and decompress an archive, place BIOS and flash dumps named dc_boot.bin and dc_flash.bin in the data folder, then choose their disc-image directory. · senryoku.github.io, 30 Sept 2026
Issue intake: Issue creation is restricted in the Deecy GitHub repository. · github.com, 1 Oct 2026
Keyboard: Keyboard bindings can be customized in Settings. · raw.githubusercontent.com, 1 Oct 2026
Known limitations: The README lists exclusion volumes and open translucent modifier volumes as missing renderer features. · raw.githubusercontent.com, 1 Oct 2026
Licensing: The rest of Deecy is MIT licensed, while included MAME data is BSD-3-Clause licensed. · raw.githubusercontent.com, 1 Oct 2026
Linux serial feature: The --scif option pipes the serial port to /tmp/deecy/scif on Linux for use with dcload-serial. · raw.githubusercontent.com, 1 Oct 2026
Linux serial integration: The Linux-only --scif option pipes a serial port to /tmp/deecy/scif for dcload-serial prototyping. · github.com, 30 Sept 2026
Maker: Sen describes himself as a software developer from France and identifies the project account as Senryoku. · github.com, 1 Oct 2026
operating systems: The official site describes Deecy as an open-source Dreamcast emulator for Windows and Linux. · senryoku.github.io, 30 Sept 2026
Product: Deecy is an open source Dreamcast emulator for Windows and Linux. · senryoku.github.io, 1 Oct 2026
product type: Deecy is an experimental Dreamcast emulator written in Zig. · github.com, 30 Sept 2026
Save states: Keyboard shortcuts provide four save-state slots and four load-state slots. · raw.githubusercontent.com, 1 Oct 2026
Support: The project directs users to the GitHub issue tracker for bug reports. · senryoku.github.io, 1 Oct 2026
Technology: Deecy is an experimental Dreamcast emulator written in Zig. · raw.githubusercontent.com, 1 Oct 2026

Where Deecy stands on Freedom251

Dreamcast Emulators#4 of 9