Adaptec 2944UW Installation Guide - Page 7

SCSI Device Settings The SCSI device settings allow you to configure certain parameters for each device on the SCSI bus. To configure a specific device, you must know the SCSI ID assigned to that device. If you are not sure of the SCSI ID, see Using the SCSI Disk Utilities on page 8. s Initiate Sync Negotiation-This option determines whether the host adapter initiates synchronous data transfer negotiation (Sync Negotiation) with connected devices. The default setting is Yes. Synchronous negotiation is a SCSI feature that allows the host adapter and its connected SCSI devices to transfer data in synchronous mode. Synchronous data transfer is faster than asynchronous data transfer. The host adapter always responds to Sync Negotiation if a SCSI device initiates it. If neither the host adapter nor the SCSI device initiate Sync Negotiation, data is transferred asynchronously. Normally, you should leave the Initiate Sync Negotiation setting enabled, because most SCSI devices support synchronous negotiation and because it allows for faster data transfer. Note: Some older SCSI-1 devices do not support Sync Negotiation. This may cause your computer to operate erratically or hang if Initiate Sync Negotiation is set to yes. Set Initiate Sync Negotiation to No for these devices. s Maximum Sync Transfer Rate-This option sets the maximum synchronous data transfer rate that the host adapter supports. The default setting is 20.0 MBytes/sec. The host adapter supports rates up to the UltraSCSI maximum of 20.0 MBytes/sec (the AHA-2944UW provides an effective maximum synchronous transfer rate of 40.0 MBytes/sec for UltraWide devices). If your device is an UltraSCSI device, you can use the maximum value of 20.0 MBytes/sec. If your device is not an UltraSCSI device select a transfer rate of 10.0 MBytes/sec. If the host adapter is set not to negotiate for synchronous data transfer (that is, Initiate Sync Negotiation is set to No), then the maximum synchronous transfer 6 rate is the maximum rate that the host adapter accepts from the device during negotiation. (This is standard SCSI protocol.) s Enable Disconnection-This option determines whether the host adapter allows the SCSI device to disconnect from the SCSI bus (sometimes called Disconnect/Reconnect). Enabling disconnection allows the host adapter to perform other operations on the SCSI bus while the SCSI device is temporarily disconnected. The default setting is Yes. s Initiate Wide Negotiation- This option determines whether the host adapter attempts 16-bit data transfer (Wide negotiation) instead of 8-bit data transfer. The default setting is Yes. Note: Some 8-bit SCSI devices have trouble handling Wide negotiation, which may result in erratic behavior or a hang condition. For these devices, set Initiate Wide Negotiation to No. When set to Yes, the host adapter attempts 16-bit transfer. When set to No, 8-bit data transfer is used unless the SCSI device itself requests Wide negotiation. The effective transfer rate is doubled when 16-bit data transfer is used because the data path for Wide SCSI is twice the size of normal 8-bit SCSI. For example, a transfer rate of 10 MBytes/sec becomes 20 MBytes/sec, and a transfer rate of 20 MBytes/sec (UltraSCSI) becomes 40 MBytes/sec. s Send Start Unit Command-This option determines whether the Start Unit Command is sent to the SCSI device at bootup (most devices do not require this). The default setting is No. Setting this option to yes reduces the load on your computer's power supply by allowing the host adapter to start SCSI devices one-at-a-time when you boot your computer. When set to no, the devices are allowed to start at the same time. Most devices require you to set a jumper before they can respond to this command. Note: If the Send Start Unit Command is set to yes for many devices, the boot time will vary depending how long it takes each drive to start.