rom_tool is a tool I wrote in light of the recently announced Gateway 3DS. It has three main features: 1  Read 3DS ROMs, and print information about them, including actual ROM file size, and minimum required 3DS FW etc. 2  Accurately trim 3DS ROMs, and be able to restore them again.uper Trim ROM (Permanently remove update partition): rom_tool-s Test.3ds. Restore ROM (Untrim): rom_tool-r Test.3ds. Supported Operating Systems: 1  Windows 32bit/64bit (Tested on Windows 7/8) (executable included in download). 2  Mac OS X (Tested on 10.8.3) (executable included in download).