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The Adaptec 2940 SCSI Host Adapter Driver supports Synchronous Data Transfer as well as Fast SCSI transfers. In order to enable Synchronous Data Transfer, this feature must be enabled in both the 2940's AutoSCSI program and in the NEXTSTEP Configure application, when configuring the Adaptec 2940 driver. In the AutoSCSI program, this feature is enabled in the SCSI Device Configuration menu, via the "Initiate Sync Negotiation" field. This can be enabled or disabled on a per-target basis. In the Configure application, the "Synchronous" button, if disabled, disables Synchronous Transfers for ALL targets. If enabled, the values selected in the AutoSCSI program are used to determine whether or not Synchronous Transfers occur on a per-target basis.
The Synchronous Transfer data rate is determined in the 2940's AutoSCSI program, via the "Maximum Sync Transfer Rate" field in the SCSI Device Configuration menu. "Fast SCSI" Transfers are enabled by selecting a value of 10 (i.e., 10 Megabytes/seconds) for this field. Note that if Synchronous Transfers are disabled, the "Maximum Sync Transfer Rate" field is meaningless. Also note that it is not recommended to select a value higher than 5 for a device which is in an external enclosure and connected to the 2940 via an external SCSI cable.