IBM SG24-4576-00 manual Bit 68pin Bit 50pin Low High

The fields on this panel are described as follows:

SCSI Parity Checking: Select this option to enable or disable SCSI Parity checking on the host adapter. If enabled, the host adapter will check parity when reading from the SCSI bus to verify the correct transmission of data from your SCSI devices. SCSI Parity checking should be disabled if any attached SCSI device does not support SCSI parity. Most currently available SCSI devices do support SCSI parity.

Host Adapter SCSI termination: All SCSI interfaces use daisy-chain 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 which 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 which 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 what 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 16. Host Adapter SCSI Termination Parameter

16-bit (68pin)	8-bit (50pin)	16-bit (68pin)	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:

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Use the arrow keys to select SCSI Device Configuration Press Enter

A screen like the one in Figure 36 on page 80 will appear:

Chapter 3. H a r d w a r e Configuration 79