Our recent article about the new AppleCD 300 had some technical holes in it which Craig O'Donnell, a resident (well, he must live somewhere) CD-ROM maven has helped to fill. Craig has reviewed CD-ROM hardware for MacWEEK for the past few years and keeps people abreast of CD-ROM developments on ZiffNet/Mac.
About the CD formats mentioned briefly in the article, Craig explained, "CD+G puts slowly scrolling graphics or "slide images" in 16 colors up on a screen - it is the Karaoke audio format and is otherwise not commercially sold. CD+MIDI is an audio CD which contains MIDI sequencer data. It is a moribund format. Both of these use the 5% of the bitstream on an audio CD devoted to "subcode." It would be more useful if they put track names and CD title in the subcode!"
In regard to Mode 2 support by the AppleCD 300, and apparently most drives, Craig says, "Mode 2 Form 1 is basically CD-ROM XA and is required for a drive to support PhotoCD, unless the driver software has been specifically written to perform "raw reads" and emulate the Mode 2 Form 1 firmware; this is how Trantor makes the old Toshiba 3201 drive read single session PhotoCDs."
Craig notes that you have to use a special write-many CD for multiple sessions of PhotoCD pictures. In addition, he says, "Commercially pressed disks are "single session" by definition. The first batch of photos on a multi-session CD - up to about 100 total - is also readable by a single session drive." This suggests that you shouldn't concern yourself unduly about multi-session capabilities when buying a drive unless you plan to store photos on CD.
About the features of the older AppleCD 150, Craig wrote, "The AppleCD 150 can read single session PhotoCD, is an excellent drive, and will be even more excellent when its price drops to maybe $459 list." This implies to me that the AppleCD 300's major advantage is its double-speed mode, which will help when the drive reads a lot of data from contiguous parts of the disc. Keep in mind though, that QuickTime appears to be written to cope specifically with 150 KB/second transfer rates in single-speed drives.
Craig O'Donnell -- firstname.lastname@example.org