IBM SG24-4763-00 manual Bit 68-pin Bit 50-pin Low High

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.

Table 1. Host Adapter SCSI Termination Parameter

16-bit (68-pin)	8-bit (50-pin)	16-bit (68-pin)	Low	High
internal connector	internal connector	external	value	value
		connector
Yes			On	On
		Yes	On	On
	Yes		On	On
Yes		Yes	Off	Off
Yes	Yes		Off	On
	Yes	Yes	Off	On

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.

14PC Server and Windows NT Integration Guide