IBM OPTIONS User Manual page 15

v ID 7 is the highest priority ID on the SCSI bus. Make sure ID 7 is assigned
to the SCSI adapter. Do not use the SCSISelect utility program to change the
ID assignment of the SCSI adapter. The priority of the other IDs in
descending priority order are 6 to 0 and 15 to 8.
v Assign higher priority SCSI ID numbers to the devices that are most often
used or are faster than other devices in the SCSI chain. (The SCSI ID
assigned to a device is not related to the order in which the devices are
attached to the SCSI adapter.)
v If you start up your computer from a SCSI device, assign SCSI ID 0 to the
startup drive. ID 0 is the SCSISelect initial setting. (If both SCSI and IDE
disk drives will be installed, you cannot start up your computer from a SCSI
device. In this case, the IDE disk drive is always the startup device.)
v Change the ID settings according to ID assignments you have chosen. Refer
to the documentation that comes with your SCSI devices for information on
how to change the SCSI ID. One way to remember the SCSI ID for each
device is to label the device. When putting the label on a hard disk drive, do
not press down on the top of the drive because the pressure might damage
it.
You can also use the following table in your planning by writing down the
SCSI ID you assign to each device. The SCSI IDs are listed in decreasing
priority order.
SCSI ID
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
Device
SCSI Adapter
Part 2: Installation and user's guide
2-3