Two drives on a PowerBook IDE bus?

I thought I’d try attaching two drives to the internal IDE bus on my PowerBook (Wallstreet). Using the IDE cable I’d constructed earlier I hooked up a 6GB hard drive set to master and a CD-ROM set to slave. The HD turned up on my desktop, but the CD-ROM didn’t. After trying a heap of different master/slave/cable combinations and not getting anywhere I decided to read the PowerBook Developers PDF. It says stuff like I/O channel select; not used on this computer and Device active or slave present; not available on this computer so it seems that the internal IDE bus will only support one drive. I’ll have to use either the SCSI bus or the expansion bay to connect a CD player.