Creating a bootable Dreamcast disc

Full Overview of the steps involved

The full list of steps to make self-bootable disc for the Dreamcast goes like this:

• Build your source (usually using KallistiOS)
• Transform your .elf executable into binary
• Scramble the binary
• Build a .iso image from a directory (representing the second session of a multisession disc and not bootable)
• Transform the .iso into a .cdi image (representing a self-booting multisession disc image)
• Transfer the .cdi image to your GDEMU (or other optical disc drive emulator device), or burn the .cdi image to a CD-R to launch it in a standard Dreamcast.

There are other details that could be taken into account:

• You can make Audio/Data and Data/Data .cdi files. Both can selfboot, but the files will be organized differently on the physical CD. ^{Citation needed}
• You'll need to provide a valid IP.BIN, these can be modified to display a logo during the boot screen, apply patches or execute some code.
• It is possible to make CDDA compatible images, this process in not currently covered here.

Depending on the method/tools used, some of the above steps are simplified a lot:

• mkdcdisc: does the heavy lifting for you. Linux only for now.
• mkisofs + cdi4dc
• mkisofs + cdrecord

mkdcdisc (Linux only for now)

mkdcdisc is a recent (2022) tool that pretty much does all the steps for you.

The minimum you need for it, is your executable .elf (or the equivalent scrambled or unscrambled bin file).

Example to build a bootable DC disc image nehe05.cdi, starting from an executable called nehe05.elf:

mkdcdisc -e nehe05.elf -o nehe05.cdi

Example to build a bootable DC disc image mygame.cdi, starting from an executable called mygame.elf, with assets/textures/... files stored in a subfolder called "data":

mkdcdisc -e mygame.elf -D data -o mygame.cdi

There are a lot of commandline options, so be sure to check them all out!

mkisofs + cdi4dc

This is an example for automating the .cdi image process under Linux. Consider this more like a template as you'll need to edit the paths, names, etc to your own project.

 #! /bin/sh
 PROJECT_DIR=$PWD/build
 PROJECT_NAME="Project_Name"
 TARGET="main.elf"

 # Build your program
 # This assumes that you can properly build your source code. The program main output will be $TARGET
 make $TARGET

 # Elf transform
 sh-elf-objcopy -R .stack -O binary $TARGET output.bin

 # Scrambling process
 $KOS_BASE/utils/scramble/scramble output.bin 1ST_READ.bin

 # Creating a .iso image from a directory 
 # Make sure you have a working IP.BIN in your current directory. Or change IP.BIN path to wherever you like.
 # Useful option for mkisofs is *-m* which allow to exclude files from the iso image (useful to remove .git, or some other folder) 
 mkisofs -C 0,11702 -V $PROJECT_NAME -G IP.BIN -r -J -l -o $PROJECT_NAME.iso $DIR

 # Transform your .iso into a .cdi
 $KOS_BASE/utils/cdi4dc/cdi4dc $PROJECT_NAME.iso $PROJECT_NAME.cdi

mkisofs + cdrecord

TODO