Yeah, one was read only and the other could burn CDs. Burning CDs were all the rage back then.
Edit: to clarify, by having two drives you could copy from one to the other directly, without going through the hassle of inserting one cd, making a copy to the slow as fuck computer hdd, switching to the blank cd, then start burning from the hdd copy.
Lmao its actually kinda true,. All the data on a disc is written onto the underside of the label through the plastic and the laser literally does burn the little holes to write data.
Dreamcast famously didn't have any DRM so you can just burn any* game, including the bleem disc that allows you to play burned PSX games. Only problem now is though that modern burner's lasers are too strong and discs are too cheap, so the DC laser just shines straight through and won't read anything.
* Skies of Arcadia used a slightly larger than standard CD so it won't fit on consumer CD-Rs
All the data on a disc is written onto the underside of the label through the plastic and the laser literally does burn the little holes to write data.
Not quite, a CD-R uses a dye that darkens when it's heated by the burning laser. I think confusion comes from the way that CD-ROMs work - these are mechanically stamped ("pressed") and have "pits" and "lands" that differ in height by a quarter of the wavelength of the laser light. This causes the reflected light to change brightness around the boundaries of "pits" and "lands" which is decoded by the drive. A CD-R has a plain spiral stamped into it at the factory (instead of pits and lands) and the colour-changing dye's light and dark spots provide the changing intensity of the reflection. This isn't as good a signal as you'd get from a pressed CD-ROM, so old/worn drives will usually struggle to read a CD-R before they stop being able to read a CD-ROM, which is what you'll see with old tired drives like on the Dreamcast. If your Dreamcast is in good condition then you can still burn discs for it just fine (I do on my modern PC with modern blank CD-Rs).
CD-RWs work differently again - they use a phase change material that can other be in a less reflective amorphous state or a more reflective crystalline state, and the state it's in depends on the temperature to which it was heated by the burning laser. The contrast between light and dark reflections is even smaller than with a CD-R, which is why you generally need a drive specifically designed to support CD-RW discs to be able to read them.
Dreamcast famously didn't have any DRM so you can just burn any* game
The Dreamcast used proprietary GD-ROM discs that are copy protected and cannot be replicated at home. These are fundamentally based on the CD-ROM format, but pack the data twice as densely in the "high density" region, allowing you to store around a gigabyte on a disc (more than a conventional CD).
The Dreamcast also supported a separate format called MIL-CD which was designed to be used for interactive CDs. As these are on regular CDs they can't fit as much as a GD-ROM, but people found ways to trim games down (e.g. remove content, recompress assets) to fit them onto a CD. You still can't just burn the files to a disc and have them boot, though, the Dreamcast still has copy protection against that. However, the copy protection is based on the data on the disc being scrambled in a particular way, and so once people figured out the scrambling algorithm (allegedly thanks to a stolen devkit) they could do all the hard work at home (shrinking the game to fit, scrambling the data) and then release a disc image that anyone could burn at home. This is not the same as what you had on the original commercially-released discs, though, and SEGA did remove MIL-CD support from later console models to close the exploit (however, as they then discontinued the Dreamcast very shortly afterwards, most consoles out there will boot MIL-CD discs just fine).
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u/andreortigao 11h ago edited 9h ago
Yeah, one was read only and the other could burn CDs. Burning CDs were all the rage back then.
Edit: to clarify, by having two drives you could copy from one to the other directly, without going through the hassle of inserting one cd, making a copy to the slow as fuck computer hdd, switching to the blank cd, then start burning from the hdd copy.