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Dreamcast Linux

Dreamcast Linux is a full Linux distribution for the Sega Dreamcast, with a Docker-based build environment for producing a minimal bootable Dreamcast Linux system.

See the latest release for the available bootable CDI images:

  • base-busybox: kernel + initrd with a minimal BusyBox shell, supporting NFS, GD-ROM mounts, and more
  • with-userland: full system with about 140 packages on GD-ROM, mounted via overlayfs. Available as musl or uclibc builds.

The image already includes a usable and up-to-date software stack, but application coverage, graphical interfaces, memory usage, and build reproducibility still need work. The patches are currently applied manually.

It is actually tested on real hardware.

Tested Devices, feel free to add PR to add your test device:

Medium Revision Works Description
GDEMU, dcload-serial, dcload-ip HKT-3030, PAL E, Rev. 1 ✔️ Yes framebuffer, serial console, network, gdrom
GDROM, dcload-serial HKT-3000, NTSC J, Ugo Denshi 670-14071E ✔️ Yes framebuffer, serial console, network, gdrom
GDROM, dcload-serial HKT-3020, NTSC U, Rev. 1 (670-14081B) ✔️ Yes framebuffer, serial console, gdrom
GDEMU HKT-3020, NTSC U, Rev. 1 (670-14081M) ✔️ Yes framebuffer, serial console, network, gdrom
GDEMU HKT-3020, NTSC U, Rev. 1 (670-14081K) ❌ stays at sega screen
GDROM HKT-3030, PAL E, Rev. 1 soon to be tested
CDI GXemul 0.7.0+dfsg ❌ No [ exception 0x160, pc=0x8c4abede vaddr=0x00000000 ] see gxemul-analyze.txt
CDI lxdream 0.9.1 ❌ No stays at sega screen, with memset/memcpy sh4-specifics removed, boots to console, but no interaction possible see lxdream-analyze.txt
CDI flycast 2.6 ❌ No stays at sega screen, see flycast-analyze.txt
CDI redream 1.5.0 ❌ No redream-analyze.txt

ATTENTION: You need to customize the .dreamcast/src/linux-xx/arch/sh/Kconfig to modify BOOT_LINK_OFFSET, aligned to .dreamcast/src/sh-boot/tools/dreamcast/kernel-boot.S L_binary_zImage_bin_dest: and L_entry:. (The memory position of the zipped kernel image, depending on how big it is). In the example below, we chose 0x00600000 / 0xac600000.

config BOOT_LINK_OFFSET
        hex
        default "0x00210000" if SH_SHMIN
        default "0x00600000" if SH_DREAMCAST
        default "0x00810000" if SH_7780_SOLUTION_ENGINE
        default "0x009e0000" if SH_TITAN
        default "0x01800000" if SH_SDK7780
        default "0x02000000" if SH_EDOSK7760
        default "0x00800000"
        help
          This option allows you to set the link address offset of the zImage.
          This can be useful if you are on a board which has a small amount of
          memory.

I use kernel-integrated initramfs and not the sh-boot initrd. The path to the initramfs is defined in the kernel-config. (CONFIG_INITRAMFS_SOURCE="/usr/src/dreamcast/initrd" )

Apply patches

dreamcast-linux/.dreamcast/src/linux-6.19.9 ❯ patch -p1 < ../../../hotfix-dreamcast-*.patch
dreamcast-linux/.dreamcast/src/linux-6.19.9 ❯ patch -p1 < ../../../hotfix-vmu*.patch
dreamcast-linux/.dreamcast/src/linux-6.19.9 ❯ patch -p1 < ../../../hotfix-gdrom*.patch

About

Creates a cross-compilation environment for the SH4 architecture using:

  • gcc
  • glibc
  • linux
  • binutils
  • busybox

Requirements

Docker on Linux.

Usage

Please inspect the local variables in the dreamcast/build-dreamcast.sh script before running this. Some options might not fit your setup.

make

You should now have the final images in build/ folder.

All building happens in .dreamcast/.

Links

License

This source is licensed under MIT. See attached licenses for third party libraries included for more information.