I allowed launching Gamecube games from USB (to work with DIOS MIOS).
I didn't change anything else in the code than adding a button to launch from USB instead of copying to SD first.
USB Loader GX r1191 with DM support.
Usage:
1. of course, Install Dios Mios
2. If you don't have it yet, set the "GC Main Path" on USB:/games/ and place your game's folder inside. (You need a FAT32 partition, not NTFS).
3. If you have both games on SD and USB, delete/rename/move the folder from SD, as it will be used in priority and DM won't work.
The games should be located in folders like this : USB:/games/
game name[ID6]/game.iso
rename only the blue part, or just dump your original game with USB Loader GX and it will create the correct folder.
4. Run the game and select "Launch from USB".
I guess you could also set the "GC SD path" to USB, but I didn't test that yet.
It was just a very quick update to prevent copying to SD before launching.
Let me know if games are working with other loaders which aren't from USBloader GX.
Thanks to Dimok too, it was easy to add USB