Compaq 159715-002 - Deskpro EN - DT 6650 Model 10000 Configuration Manual page 135

Every SCSI chain or circuit must be terminated (closed) at
both ends. Termination can be accomplished by using the
terminating feature on the device or by using a terminated
cable.
Some devices may not have terminating jumpers on the
device. Termination on these devices must be achieved
with terminated cable.
Turn on an external SCSI device before turning on power
to the computer. This enables the system board controller
to recognize the external SCSI device and automatically
reset. When an external SCSI device is connected to the
external SCSI connector on the rear panel of the
computer, that device becomes the end of the SCSI chain
and must be terminated.
The system accommodates a combination of internal and
external SCSI devices, such as SCSI tape, CD-ROM drives,
and hard drives.
When an IDE hard drive and SCSI hard drive are both
installed, the system can boot only from the IDE hard
drive.
Before you can install a SCSI device, you must first
verify the SCSI ID of the device and, if necessary, set the
SCSI ID to a new number. Be sure that each SCSI device
on the SCSI chain has a unique SCSI ID number.
Second, you must determine if the device ought to have
termination enabled or disabled. Set the termination if
necessary.
Making Hardware Changes C-3