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This soft copy for use by IBM employees only.
2 Host Adapter SCSI Termination
All SCSI interfaces use daisy-chained cabling. The cable starts at the
adapter and goes to the first device, and then out of that device to the next
device and so on until it reaches the last device in the chain. The last
device has an incoming cable and a
terminator
. The terminators are used to
absorb potential signal reflections on the SCSI bus that would cause
interference. The last device on the bus must always be terminated.
The SCSI-2 Fast/Wide PCI adapter that came with the PCI/EISA server has
three connectors that can be the starting points for a daisy-chained cable:
one 8-bit, 50-pin (SCSI-I) internal connector, one 16-bit, 68-pin (SCSI-II Wide)
internal cable connector, plus another 16-bit, 68-pin external connector. The
adapter has built-in terminators on these connectors.
The setting for the Host Adapter SCSI termination needs to be configured
depending on which connectors are used. This option is comprised of two
entries, a low and a high. You can think of them as software jumpers. Each
entry, low and high, can take on either an on or off value, thereby giving four
possible different combinations of the two entries. The chart below shows
the proper values of these entries depending upon which connectors have
been used.
Note
Only two of the three connectors can be used, either the two internal or
one internal and one external.
After configuring the host adapter, you need to configure the SCSI devices. To
do this, from the panel shown in Figure 8 on page 13:
•
Use the arrow keys to select SCSI Device Configuration.
•
Press Enter.
A panel similar to the one in Figure 9 on page 15 will appear.
Table 1. Host Adapter SCSI Termination Parameter
16-bit (68-pin)
internal connector
8-bit (50-pin)
internal connector
16-bit (68-pin)
external
connector
Low
value
High
value
Yes On On
Yes On On
Yes On On
Yes Yes Off Off
Yes Yes Off On
Yes Yes Off On
14 PC Server and Windows NT Integration Guide