DreamCast Console - Page 2

Behind the protection scene

What is a GD-ROM CD?

GD-ROM (Giga-Byte Disk) is a CD format developed by Yamaha. The GD-ROMs can save up to 1GB of data (in contrast to the normal CD-ROMs which, depending on the data format used, can theoretically hold 90 minutes of information). This method presumably works on the principle that the individual pits are packed more closely than is usual with CD-ROMs. GD-ROMs are used by the games consoles developed by SEGA called DreamCast. The game console uses a 12x GD-ROM drive by Yamaha.

The back of a GD-ROM consists of 3 separate areas:

- The inner area with normal write density which can record up to approx. 35MB (4 minutes) of data. This area can be read by a normal CD-ROM drive. This area consists of two tracks. A data track Mode1 and an audio-track, which an audio CD player can play. The respective tracks must be at least 4s long.
- The outer area with a high write density which can record approx. 1GB (112 minutes) of data. This area can not be read by a normal CD-ROM drive or CD burner. This area also consists of 2 tracks. This area is written in so-called CAV-mode. Based on information received, the additional available memory space is also achieved by writing information in areas which are normally not used.
- Between the outer and the inner area is a blank, unwritten layer which serves as a border between the areas. This area contains the lettering: "..Produced by or under license from sega enterprises LTDs. Trademark SEGA.."

Can i backup GD CDs?

No. GD CDs can not be copied or written with normal CD burners.

Can DreamCast CDs backuped with a DVD-R?

Not really..DVD-R/RWs like the CDR-W and CD-Rom cannot read the second session of the GD CD!

Why this happens? What is the protection scene behind?

A GD CD contains more information than a normal CD-R/RW (112+4 instead of 90 minutes). Sega uses special writable media. However are only sold to official DreamCast developers and are not available to the general public. And anyway, a GD burner would be necessary. Also the two sessions are separated with a large visible space. This is made in propose so the laser beam couldn't  even accidenlty reach the second session and read it. The real problem is the second session, since with normal CDR-W and CD-Rom drives you cannot read it. Finally, the DreamCast console has extra protection for GD CDs backups but not for normal CDs. This was used from the Utopia group in order to make their BootDisc, which used for booting backup images, which is a mode2 CD.

How can the DreamCast read CDs? As far i know no other console allows that!

DC does prevent the reading of copied GD-ROMs since it had build-in checks for it, but this doesn't happen with normal CDs. DC does have that check, but only for GD-ROMs. DC software can read any normal CD-ROMs it pleases. But this will not happen with  PSX/PS2/Saturn consoles since you'll get a read error if you try to read a CD that doesn't pass the protection checks.

Hmm..Why DC allows reading of normal CDs since the Sega's Saturn console had this protection?

I think the most appropriate person to answer that question is the Sega design team. However we can image a little story about this...Do you know what is this "Bleemcast" about? BleemCast is the first emulator for DC which can play PSX CDs. Bleemcast can exist *ONLY* because of the lack of that protection. If it were locked out, Bleemcast couldn't exist because it wouldn't be able to read PSX CDs!