In order to help prevent alpha and beta games being leaked to the public, Sega made sure that an additional disc was required to run developer burned GD-Rs.
This additional disc was known as the Sega Dreamcast System Disc 2.
In order to run any developer-burned games you would need to insert the disc into either a standard dreamcast or development kit which would then ask for the burned disc to be inserted.
This additional layer of security helped game development studios put their mind at ease when sending prototypes or final review candidates to third parties such as games magazine publishers for review.
The GD-R discs are writeable versions of GD-ROMs and are burned by developers using their Dreamcast development kits
DEV.BOX using a program called the