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ULTRA2 LVD SCSI HOST ADAPTER
4.2 Attaching Other SCSI Devices to the Adapter’s Bus
You can connect as many as fifteen internal and external SCSI devices to your
Ultra2 LVD SCSI Host Adapter. Follow the directions listed in this section. (If you
are connecting SCSI devices to multiple Adapters to form a clustered system, refer
to Section 4.5.)
4.2.1 C
ONNECTING
I
NTERNAL
SCSI D
EVICES
If you are connecting internal SCSI devices, make sure to use a SCSI ribbon cable
that (a) is not too long (see Section 3.3), (b) has the appropriate characteristics
(see Section 3.3), and (c) has enough connectors to accommodate the Adapter
and all of your internal peripherals. Figure 4-3 below shows the preterminated
Wide (68-pin) internal cable that comes with the Adapter; it has enough
connectors for four internal SCSI devices.
Figure 4-3. The Adapter’s included internal ribbon cable.
This cable is 125 cm (4.1 ft.) long; whether you use it or some other cable, keep
in mind that the total length of cable on the Adapter’s SCSI bus, including both
internal and external cables, mustn’t exceed 12 m (39.4 ft.) unless you’re attaching
one and only one peripheral, in which case you can run as far as 25 m (82 ft.). And
this assumes that all of your devices are Ultra2 SCSI LVD compliant; if you are
attaching any legacy devices, the maximum total bus length will be much less:
• 6 m (19.7 ft.) if the only legacy devices attached to the bus are SCSI-1 or Fast
SCSI (SCSI-2) devices.
• 3 m (9.8 ft.) if you have four or fewer devices attached to the bus and any of
them are Ultra SCSI (SCSI-3) devices.
• 1.5 m (4.9 ft.) if you have five or more devices attached to the bus and any of
them are Ultra SCSI (SCSI-3) devices.
The cable should have an impedance of at least 120±8 ohms if any Ultra2 SCSI
LVD devices are attached; the impedance can be as low as 90±8 ohms only if all
attached devices are non-Ultra2-type.
Connect
to the
Adapter
Connect 2nd
SCSI device
here
Connect 1st
SCSI device
here
Built-in
Terminator
(Connect remaining
SCSI devices to other
intermediate connectors)