SCSI Jumpers
The option jumper block on the DASD (SCSI) backplane defines the SCSI IDs for
hot-swap drives. See the illustration in “DASD Backplane Jumper Block Location”
on page 174 for the location of the option jumper block.
Table 19 summarizes the settings for the DASD backplane SCSI option jumper
block (J4).
Table 20 shows the SCSI IDs that you can use for hot-swap drives.
Table 19. Backplane Option Jumper Block
Pins
Description
1-2 (A0)
Removing the jumper from these two pins reverses the SCSI IDs on the
backplane. For the tower model, these two pins are jumpered; for the rack
model, the jumper usually is removed.
3-4 (A1)
Reserved. No jumper.
5-6 (A2)
These pins are always jumpered.
Tower Addressing
Rack (Reversed)
Addressing
J4
A2
A1
A0
J4
A2
A1
A0
Table 20. SCSI IDs for Hot-Swap Drives
J4 Pins 1-2 (A0)
Bay 1
Bay 2
Bay 3
Bay 4
Bay 5
Jumpered (tower
orientation)
0
1
2
3
4
Jumper removed, DASD
enclosure not rotated
4
3
2
1
0
Jumper removed, DASD
enclosure rotated for rack
orientation
0
1
2
3
4
Notes: When the DASD enclosure on a tower model has been rotated for rack-mount orientation
and the jumper has been removed, the bays correspond to the rack model illustration on page 56.
Chapter 7. Server Records and Specifications
173
