NEC MH4000, User Manual

Page: 172 / 204

A-2
System Cabling
Standard SCSI Bus Configuration
Your system is cabled using the two on-board SCSI
controllers. The on-board Adaptec 7880 ultra wide SCSI
controller is used to control the six hard disk drives
and the on-board Adaptec 7860 narrow SCSI controller
is used to control up to three removable media
peripherals (CD-ROM and tape drives). A 3 1/2-inch
diskette drive is installed in all systems and interfaces
separately to the system board. Figure A-1 is a diagram
of the standard SCSI cabling and Figure A-2 illustrates
the internal cable routing for this configuration.
The narrow SCSI interface cable is connected to the
SCSI connector on the top edge of the system board (see
Figure A-1, D). This cable connects to the rear of the
SCSI removable media peripherals (if present). The last
drive on the daisy chain cable must have it’s internal
SCSI terminators installed.
The ultra wide SCSI interface cable is connected to the
SCSI connector on the lower right-hand side of the
system board (see Figure A-1, I). This cable connects to
the SCSI distribution panel at the rear of the hard disk
drives (see Figure A-1, K). Termination for the hard
disk drives is provided on the SCSI distribution panel.
The onboard narrow SCSI controller also includes a
connector located at the rear of the system for
connecting external SCSI devices. Three important
rules must be followed if you connect external narrow
SCSI devices:
■
A maximum of seven narrow SCSI devices may be
connected to the onboard SCSI controller. For example
if three SCSI devices in the system cabinet are
connected to the SCSI bus, only four external narrow
SCSI devices can be connected.
■
The maximum cable length for all narrow devices
connected to the controller is 1 meter (39 inches).
■
The last external narrow SCSI device must be
terminated. Active termination is recommended.