Dump and restore GB/GBC cartridges via GBA multiboot
Power on the GBA without a cartridge inserted, then click "Send Multiboot". After the multiboot completes and the GBA switches to GBC mode, insert your GB/GBC cartridge. Some cartridges have a voltage supervisor that resets the GBA on insertion — placing a small piece of kapton tape over pin 30 (/RESET, 3rd pin from the right) on the cartridge prevents this. Inserting slowly can also help. Once the cartridge is detected, press:
"Send Multiboot" loads the dumper ROM onto the GBA, then waits — press a button on the GBA to dump, or use the Restore section below. Click "Homebrew Already Loaded" instead to skip the multiboot when the GBA is already running the dumper ROM (e.g. after a previous dump).
This overwrites the save on the cartridge. Make sure the
GBA is already running the dumper ROM (use "Send Multiboot"
first if not), then load a .sav file below,
click "Restore Save", and when prompted press SELECT on
the GBA. The file's size must exactly match the cart's SRAM, or
the restore is refused.
Idle
Disconnected