DVD_Mode was used in the V4 Pre-Boot environment to deal with devices having the EHCI USB controller in a particular case where the controller might not report or interface with some tokens correctly if a DVD device is inserted. This option is rarely used anymore. Advances in BIOS and EHCI controllers in recent years have made this setting unnecessary in most (if not all) cases. This option is currently retained for backward compatibility, and might be deprecated in a future version.