Interestingly, The Dreamcast's GD-ROM format was nonstandard enough to not be copyable with a normal CD burner, at least at first. They used CAV + cutting the d

Interestingly, The Dreamcast's GD-ROM format was nonstandard enough to not be copyable with a normal CD burner, at least at first. They used CAV + cutting the disk speed in half in order to write more data (up to 1.2GB). https://en.wikipedia.org/wiki/GD-ROM https://en.wikipedia.org/wiki/GD-ROM I think what you are referring to is the fact that the Dreamcast itself didn't only read from GD-ROM- it was perfectly happy to execute code from a CD-ROM via the MIL-CD format. > The "foot in the door" came from a seemingly obscure capability of the Dreamcast to boot not from a GD-ROM but from a CD-ROM. Originally intended to add multimedia functions to music CDs, the functionality called "MIL-CD" was never used much, accounting for a mere seven karaoke applications. [1] Which meant if you were able to acquire a GD-ROM image, and you could repack it into the CD-ROM's max capacity of some 650MB, then you could burn it to disc and play it without any modification of your Dreamcast, at least once the other protections were defeated. For games that actually utilized more than a CD's worth of data, usually pirates would recompress or remove images, video files and other assets to save space. So that copy of Sonic might not behave exactly the same as a genuine copy, simply by the necessity of the format (not that I know if Sonic required this sort of rework). Fascinating post from Fabien Sanglard for this: [1] https://fabiensanglard.net/dreamcast_hacking/ https://fabiensanglard.net/dreamcast_hacking/