HP Array Controller HSG V8.7 Software - Manual (Page 109)

Single-Ended I/O Module
UltraSCSI RAID Enclosure 5–7
See Table 5–1 for possible causes of TERMPOWER problems.
Removing an I/O module disconnects the SCSI bus termination,
resulting in a loss of TERMPOWER available to the internal SCSI
bus. Without TERMPOWER, the bus cannot function correctly.
Rules for Expanding an UltraSCSI Bus
By connecting the master enclosure to one or two expansion
enclosures, each SCSI bus is expanded from a 4-device bus to an 8- or
12-device bus, respectively. See Chapter 4 for a discussion of valid
enclosure SCSI bus addresses and the associated array controller and
storage device SCSI bus IDs.
Note
Wide UltraSCSI supports a maximum of 16 devices per bus
(2 array controllers and 14 disk drives). However, Compaq
does not support any configuration with more than 12 disk
drives.
To expand a SCSI bus, use the 68-pin VHDCI receptacle connectors
on the I/O module and a BN37A series cable. See Table 5–2 for a list
of the rules for expanding an UltraSCSI bus.
Table 5–1 TERMPOWER Problems
TERMPOWER Error Possible Causes
Internal I/O module
Power supply
External I/O module
Power supply
External SCSI bus cable