20 ST11950 and ST12550 Installation Guide, Rev. D
Setting the SCSI ID jumpers
Each device on the SCSI chain must have a unique SCSI ID. The host system’s SCSI controller usually uses the
Note. Most SCSI controllers (host adapters) allow you to skip a SCSI ID. For example, you can have ID0, ID1, and ID3 (skipping ID2). Other controllers do not allow this so be sure to refer to your system or controller user’s manual for details about its re- quirements for proper SCSI device installation.
Use connector J4 to set the SCSI ID on ST11950N/ND and ST12550N/ND drives (Figure 3). Use connector J5 to set the SCSI ID on ST11950W/WD and ST12550W/WD drives (Figure 4). Most Barracuda 1 and 2 disc drives are factory set with the SCSI ID set at 0. To change the SCSI ID, install jumpers on the appropriate pins as shown in the illustrations.
If, after completing the installation process, the drive’s LED does not show on/off activity when the host is trying to communicate with the drive, a duplicate SCSI ID may be the problem. If this is the case, change the ID so that each device on the SCSI chain has its own unique ID.