Data General AViiON 4600 Series, Customer Documentation

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Setting Up and Installing a SCSI Bus
4-6
014–002091
SCSI Bus Cabling Rules
The cabling for a SCSI bus begins inside the computer unit at the SCSI controller and
connects the mass-storage devices on the bus in a cabled daisy chain. The maximum
length of combined internal and external SCSI bus cabling cannot exceed 19.6 feet per
controller. When you calculate the total length of the SCSI bus cabling in your system,
consider the following:
•
Your system's first connector (SCSI A) supports an external SCSI bus with a cable
maximum of 14.85 feet. Of the 19.6-foot cable maximum, 4.75 feet resides within
the AViiON 530 or 4600 series computer unit.
•
An optional I/O expansion board contains a second SCSI controller and a bus
connector (SCSI B) that supports an external SCSI bus with a cable maximum of
18.6 feet. Only 1 foot of the 19.6-foot cable maximum resides within the
AViiON 530 or 4600 series computer unit.
•
Some peripheral SCSI devices consume internal cable, further reducing the
maximum length of your cable configuration. For example:
The Model 10565 PHU uses 2.75 feet of internal SCSI cable.
The CSS2/DC uses 4.83 feet of internal SCSI cable.
The G6587 reel tape drive uses 0.5 feet of internal SCSI cable.
The G6589-A and G6589-TA reel tape drives each use 0.34 feet of internal
SCSI cable.
Figure 4Ć3 illustrates the SCSI bus cable requirements.
SCSI A bus: 4.75 + 10 + .5 = 15.25 feet.
Rear panel
connector(s)
SCSI B bus: 1 + 5 + 2.75 + 1.3 + 2.75 = 12.8 feet.
Controller 0
4.75 ft. internal
bus cable
10 ft.
1.3 ft.
5 ft.
2.75 ft. 2.75 ft.
Controller 1
1 ft. internal
bus cable
Figure 4-3 Daisy Chain and SCSI Bus Cable Lengths