Technical information

If you install additional SCSI devices, you must set a
unique ID for each SCSI device that you connect to the
integrated SCSI-2 connector. This unique ID enables the
UltraSCSI controller to identify the devices and to prevent
two devices from sending or receiving data on the SCSI
bus at the same time. SCSI devices use a variety of
methods to set the SCSI ID, such as jumpers,
thumbwheels, or switches.
The SCSI device ID is also known as the SCSI
address or
physical unit number (PUN).
The UltraSCSI controller in the server supports SCSI IDs 0
to 15; ID 7 is reserved for the controller. The default
startup (boot) SCSI ID is 0 for an internal SCSI hard disk
drive in Channel A. Use SCSISelect to view the SCSI IDs
of SCSI devices in the server. (See “SCSISelect Utility” on
page 42 for more information.)
If you install wide (16-bit) SCSI devices, you can set the
IDs to any whole number between 0 and 6, or between 8
and 15. If you install narrow (8-bit) SCSI devices, you can
set the IDs to any whole number between 0 and 6.
SCSI Logical Unit Number: Each physical device
has a physical unit number (PUN) and a logical unit
number (LUN). If a physical device supports no logical
devices, its LUN is 0. Most SCSI devices support only
LUN 0. Certain types of physical SCSI devices ( bridge
controllers ) can support more than one logical device.
For example, a printer controller might support up to eight
printers. The printer controller is a physical device, and
each printer is a logical device. If the printer controller is
assigned to ID 2, the ID of the first printer appears in the
SCSI device configuration as PUN 2, LUN 0. The IDs of
the other printers are PUN 2, LUN 1; PUN 2, LUN 2; on up
to PUN 2, LUN 7.
Termination Requirements: All Netfinity 3500
servers come with an UltraSCSI controller on the system
board. This UltraSCSI controller provides termination for
one end of the SCSI bus and the cable provides
termination for the the end of the SCSI bus. Any SCSI
devices that are installed must have their termination set to
Disabled.
 When you install devices in bays 2, 3, 5, and 6, you
must disable the termination for the devices before
you install them.
 If you connected external SCSI devices to the server,
set the termination for the last device on the external
cable to Enabled. See the device documentation for
instructions.
Refer to the instructions that come with the SCSI device
for more information about termination.
IBM Netfinity 3500 - Type 8644
69