Appendix C 135
SCSI Connections
SCSI Bus Differences
SCSI Bus Differences
A SCSI (Small Computer Systems Interface) bus is an IEEE standard bus for connecting a
workstation to internal and external SCSI devices running at different speeds. There may
be one device connected to the external SCSI port, or several SCSI devices may be
daisy-chained together and connected to the external SCSI port. Examples of these SCSI
devices are 4 mm DDS-format tape drives, CD ROM drives, and hard disk drives.
The J6000 has a single dedicated external SCSI buswhich supports both low voltage
differential SCSI (LVD) and single-ended SCSI. The J6000 will also support wide (68 pin)
or narrow (50 pin via a 68-50 pin adapter cable) SCSI. The following table shows the
speciļ¬cation differences between these SCSI buses.
CAUTION
Do not mix SE and LVD SCSI devices on the same SCSI bus as this can cause
reduction in device performance.
CAUTION
A narrow SCSI device can not be placed between two wide devices.
Table C-1. SCSI Bus Differences
SCSI Type Transfer Rate Data Bus
Width
Maximum
Addresses
1
1. Address 7 is reserved for host controller use on all SCSI buses.
Maximum
Cable
Length
NSE Up to 20 MB/sec 8 bits 0 through 6 3.0 meters
(9.84 feet)
UWSE Up to 40 MB/sec 16 bits 0 through 6
8 through 15
3.0 meters
(9.84 feet)
LVD Up to 80 MB/sec 16 bits 0 through 6
8 through 15
12 meters
(39.37 feet)
