Boss MD-500

Connect MD-500 via USB while holding the RATE/VALUE knob, then attach the USB cable and plug in the INPUT jack. The device mounts as a drive called 'BOSS_MD500'. Copy MD500ROM.BIN and ROMINFO.TXT from the extracted ZIP to the root of the drive. Eject the drive, disconnect USB, then press the EDIT button on the unit to execute the update. Do not power off during the update.