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Bootroms

Attribution

The bootrom source code here has been adapted from the SameBoy project The MIT license is included in these files.

Compilation

Bootrom compilation follows the same approach as SameBoy.

The following tools and libraries are required to build bootroms:

The Makefile contains to following targets:

  • default compiles dmg_boot.bin, cgb_boot.bin and sgb_boot.bin and concatenates them into cgb_boot.mif
  • bootroms compiles all default binaries as well as mgb_boot.bin, cgb0_boot.bin and sgb2_boot.bin
  • checksum compiles a program to calculate simple checksums of binary files
  • all all of the above
  • clean delete all bootroms and object files, as well as cgb_boot.mif

Checksum

A tool is provided to calculate the checksum of a binary file. These checksums are used in the core to verify if the enhanced boot features are available.

Note: If these bootroms are edited and recompiled in future, the checksums should be recalculated and updated in Gameboy.sv

Enhancements

For convenience, two enhancements have been added to the bootroms which enables the on-screen display to change the default boot behaviour without the user needing to load a new bootrom.
Some of these enhancements extend to alternative roms in the binary folder

Fast boot

Fast boot skips the boot animation for the following bootroms:

  • cgb_boot.bin (built-in)
  • cgb0_boot.bin
  • dmg_boot.bin (built-in)

AGB emulation

The Game Boy Advance had a slightly different CGB bootrom, which enabled special features in a small number of games. AGB emulation is available for:

  • cgb_boot.bin (built-in)
  • cgb0_boot.bin
  • The original CGB bootrom (not provided)