IBM OPTIONS, Руководство пользователя

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SCSI device settings
The SCSI device settings enable you to configure certain parameters for each
device on the SCSI bus. To configure a specific device, use the SCSI ID
assigned to that device. If you are not sure of the SCSI ID, see “SCSI disk
utilities” on page B-6.
v
Initiate sync negotiation - Synchronous negotiation is a SCSI feature that
enables the adapter and its attached SCSI devices to transfer data in
synchronous mode. Synchronous data transfer mode is faster than
asynchronous data transfer. This option determines whether the adapter
initiates synchronous negotiation between the device and SCSI adapter. The
initial setting is Yes (enabled).
– Normally leave this option enabled (Yes); most SCSI devices support
synchronous negotiation, because it provides data transfer.
– Some older SCSI-1 devices do not support synchronous negotiation. This
might cause your computer to operate erratically or to stop responding if
this option is set to Yes. Set this option to No (disabled) for these devices.
The SCSI adapter always responds to synchronous negotiation if the SCSI
device initiates it. If neither the SCSI adapter nor the SCSI device initiate
synchronous negotiation, data is transferred asynchronously.
v
Initiate Wide negotiation - This option determines whether the SCSI
adapter initiates 16-bit data transfer (Wide negotiation) instead of 8-bit data
transfer. The effective transfer rate is doubled when 16-bit data transfer is
used, because the data path is twice the size of normal 8-bit SCSI. For
example, a transfer rate of 20 MB
2
/sec becomes 40 MB/sec. The initial
setting is Yes (Enabled).
– When this option is set to Yes, the SCSI adapter attempts 16-bit transfer.
– Some 8-bit SCSI devices might be unable to handle Wide negotiation; this
might cause unpredictable problems or the computer to stop responding.
For these devices, set this option to No.
– When this options is set to No, 8-bit data transfer is used unless the SCSI
device itself requests Wide negotiation.
v
Maximum sync transfer rate - This option sets the maximum synchronous
data transfer rate that the SCSI adapter supports. The initial setting is 20
MB/sec. This setting supports an effective rate up to the UltraSCSI
maximum of 160 MB/sec with 16-bit, Wide transfers.
– If your device is a Wide UltraSCSI device, you can use a maximum rate
of 40 MB/sec.
– If your device is not Wide UltraSCSI device, select a lower transfer rate
that is compatible with your device.
– If this option is set to No, the maximum synchronous transfer rate is the
maximum rate that the adapter accepts from the device during
negotiation.
Appendix B. Using SCSISelect
B-3