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GBAiD stands for GameBoy Advance in D. I've started this project as an effort to learn the D programming language.

This emulator is written mostly in pure D, with some inline x86 (32 and 64 bit) assembly in the graphics to help with performance.

Compiling works on OS X and Windows (and likely on Linux), but due to bugs with DMD, it won't compile in release mode and linking is broken on Windows.

Current state

All of the GameBoy's built-in hardware has been implemented, with the exception of sound.

I've tested 8 games so far:

  • Super Mario Advance
  • Mario kart
  • Pokemon Emerald
  • Legend of Zelda: A Link To The Past
  • Legend of Zelda: Minish Cap
  • Doom
  • Classic NES Series: Super Mario Bros
  • Classic NES Series: Metroid

Mario Kart exhibits some light graphical glitches due problems with timings (this also affects the world map in LoZ).

The Classic NES Series games load, but are very glitchy. Considering the anti-emulation features implemented in them, just the fact that they load is a good thing.

The emulator uses just under 50% CPU on my 2.66GHz dual core i7 (4GB RAM), at 60 FPS.



GBAiD uses SDL2 for input, OpenGL graphics, sound (eventually) and controller support.

  • SDL 2.0.3 or greater is required
  • OpenGL 2.0 or greater is required


First install the DUB package manager if you haven't already. GBAiD is officially built using LDC, which should also be installed.

Then use:

dub build --compiler ldc2 --build release



dub run --compiler ldc2 --build release -- (arguments)

Or get the binary from the bin folder after building and use:

./gbaid (arguments)


At minimum, you must specify the path to the bios and rom images with

-b (path to bios) (path to rom)

The following arguments are also recognized:

Long form Short form Argument Usage
--bios -b Path to bios Specify bios image
--save -s Path to save Specify path for loading and saving saves
--noload -n None Don't load the save
--nosave -N None Don't save the save
--scale -r Scaling factor (float) Draw the display at "factor" times the original resolution
--filtering -f LINEAR or NONE What technique to use to filter the output texture to be drawn to the screen
--upscaling -u EPX, XBR, BICUBIC or NONE What technique to use to increase the resolution of the drawn texture
--controller -c None Disable keyboard input and use a controller instead
--memory -m See saves section What memory configuration to use for the save format

Note that these arguments are case sensitive and that bundling is only supported by the noload and nosave switches.


Saves use a custom format and .gsf extension that is not compatible with other emulators. If no save path is specified, the same path as the ROM is used, but with the .gsf extension instead of whatever the ROM image is using. If no save is found matching either the given or default path, then a new save is created using that path. Saves are overwritten on exit, unless the --nosave argument is used.

The emulator can almost always auto-detect the save type, but for some games, such as the Classic NES Series, this will not work. Instead, the --memory flag should be used, with one of the arguments from below.

Argument Description
SRAM 64K of static RAM
SRAM_EEPROM 64K of static RAM and an EEPROM
FLASH64K 64K of Flash
FLASH64K_EEPROM 64K of Flash and an EEPROM
FLASH128K 128K of Flash
FLASH128K_EEPROM 128K of Flash and an EEPROM
AUTO Auto-detect, default

For Classic NES Series games, use EEPROM

These flags are only needed when creating a new save, after that the format is saved in the save file.


These will be re-mapable soon.

Gamepad Keyboard Controller
Up W D-pad or L-stick
Down S D-pad or L-stick
Right D D-pad or L-stick
Left A D-pad or L-stick
R R-shift RB or RT
L L-shift LB or LT
Start Enter Start
Select Tab Select


All upscaling is implemented as OpenGL shaders.

  • EPX is a simple but fast 2x upscaler.
  • XBR is a 5x implementation, it gives better results, but is slower.
  • BICUBIC is an interpolation method that offers better results than linear filtering at a greater cost. It upscales to whatever is defined by the --scale switch so it should always be used with this method.

    When you use the --upscaling switch you should also use the --scale switch with the appropriate factor for the selected algorithm.


GBAiD is licensed under MIT

Useful information

This page for a whole lot of detailed information on the hardware.

This and this for a list of all instructions supported by the ARM7TDMI CPU.