SCSI Disk Mode
SCSI Disk Mode is a function implemented into some SCSI equipped Macintosh PowerBooks. In SCSI Disk Mode the PowerBook's harddisk can be accessed as an external storage device from the host. It is by far the fastest option to access the contents of the storage media in a PowerBook from another computer. This function is triggered just by using an appropriately configured PowerBook SCSI adapter to connect the PowerBook to a SCSI host. Adaptors are available configured to boot the PowerBook into SCSI Disk Mode, to connect other peripherals to a commonly booted PowerBook, or with a switch to choose either function. Opposite to SCSI Disk Mode, a commonly booted PowerBook itself serves as SCSI host and accepts other SCSI peripherals like storage media, scanner, display adapters, network adapters or another PowerBook (which has to be booted into SCSI Disk Mode).
Macintosh Computers which support SCSI Disk Mode
SCSI Disk Mode is available in the PowerBook 160, 160c, 180, 180c, the PowerBook 5xx series, the PowerBook 1400 series and probably some other PowerBooks with inbuilt SCSI connectivity. The PowerBook 150 does not support SCSI Disk Mode. The PowerBook 1400 series computers must not be used in SCSI Disk Mode when eqipped with a storage media with a capacity of more than 4 GB, or data curruption may occur.
Setting the SCSI ID Number
The SCSI ID Number of the Macintosh computer booted into SCSI Disk Mode has to be set using a control panel, before booting into SCSI Disk Mode. Any desired SCSI ID number from ID1 up to ID7 can be assigned, leaving ID0 for the external host adaptor. The SCSI ID number should be chosen with respect to the ID numbers already assigned to other devices in the same SCSI bus, to avoid address conflicts.
Hint regarding recent Macs
In recent Macs the equivalent to SCSI Disk Mode is called Target Disk Mode. It is available in Macs that are natively equipped with FireWire or Thunderbolt ports (not limited to laptop computers). In these computers the Target Disk Mode can be triggered by depressing the "T" key during startup, or by choosing the option to boot into Target Disk Mode in the Startup Disk settings (if available).