Deecy

Deecy is a very experimental Dreamcast emulator written in Zig.

Videos: Soul Calibur (May 2024), Grandia II (July 2024)

Build and Run

Install the correct zig version (see .zigversion). You can use zigup to manage your installed zig versions.

zigup 0.13.0-dev.351+64ef45eb0

git clone --recurse-submodules https://github.com/Senryoku/Deecy     # Clone the repo and its submodules
cd Deecy
zig build run                                                        # Build and run in debug mode without any argument
zig build run -Doptimize=ReleaseFast -- -g game/game.gdi             # Build and run in release mode and loads a gdi

You will also need to provide copies of dc_boot.bin and dc_flash.bin files in the bin/ directory.

Linux

Linux isn't fully supported yet. nfd-zig (native file dialog) needs these additional dependencies on Linux:

sudo apt install librust-atk-dev
sudo apt install libgtk-3-dev

Things I know I have to do

Debug, debug, debug.
Better low level emulation: Most games do not work as well when not using the HLE'd syscalls.
ch0-DMA and ch1-DMA?
What's "Maple V blank over interrupt"? "This interrupt is generated when a Maple interface transmission/reception operation spans V-Blank_In."
AICA:
- Stereo debugging
- DSP
- More debug
Renderer:
- Framebuffer:
  - Somehow detect writes to framebuffer and display it.
  - Write back for games that need it.
- Modifier Volumes.
  - Implemented: Inclusion volumes and shadow bit over opaque geometry.
  - TODO: Exclusion volumes.
  - Test polygons with 'Two Volumes' (another way to use the modifier volumes).
  - "Region Array Data Configuration" (written by the CPU directly to VRAM) are completely ignored. I don't know if it's actually used much.
- Fog LUT Mode 2.
- Secondary accumulate buffer (very low priority, not sure if many games use this feature).
- Bump mapping.
- Handle and generate Mipmaps.
- Sort-DMA?
- User Tile Clip, only the simplest version is supported.
Ikaruga need some sort of MMU support :( Apparently only around the Store Queue, but I'm still unsure how much of the MMU I need to implement to circumvent this (and the interpreter is already painfully slow).

Nice to have

Save states
Display VMU animation :^)
Some (rendering) performance metrics directly in the emulator?
GDROM-DMA: Uses a superfluous memcpy (gdrom -> dma-queue -> ram). Not a huge deal on my main system, but I bet it's noticeable on lower end devices.

Things I don't know I have to do

A lot more than the previous list

Some sources

http://www.shared-ptr.com/sh_insns.html
SH4 Hardware Manual / Programming Manual
https://segaretro.org/Dreamcast_official_documentation
Dreamcast Programming by Marcus Comstedt : https://mc.pp.se/dc/
Boot ROM disassembly by Lars Olsson (https://lars-olsson.sizious.com/, originally https://www.ludd.ltu.se/~jlo/dc/)
AICA ARM7 Core tester by snickerbockers: https://github.com/snickerbockers/dc-arm7wrestler/
Reicast https://github.com/skmp/reicast-emulator

Dependencies

Multiple libraries from https://github.com/michal-z/zig-gamedev, included in libs/ as a submodule.
ndf-zig: https://github.com/fabioarnold/nfd-zig

Thanks

Huge thanks to drk||Raziel and MetalliC for their respective contributions to the scene, and for answering my questions!
Thanks to originaldave_ for the sh4 tests (https://github.com/SingleStepTests/sh4)
And overall thanks to everyone participating in the EmuDev Discord :)

Licence

Uses data from MAME under the BSD-3-Clause licence (see src/gdrom_secu.zig).

Senryoku / Deecy

readme