Isn't that limit when referring to the gray powerbooks (pre-Wallstreet) with IDE drives being used in SCSI disk mode? I think that was a ROM issue. greater than 4GB PB internal IDE drive = Can't be used in SCSI disk mode.

SCSI to IDE adaptors are limited only by the controller's capabilities (137GB), but some will have 48-bit LBA, which has a much higher limit.

In practical terms, it's the OS that will limit drive size. None of the PPC Powerbooks have a SCSI Internal drive (except an upgraded 5xx).