Dell PowerEdge 4400 - Manual (Page 63)

mode. Synchronous data transfer is faster than asynchronous data transfer.
The host adapter always responds to synchronous negotiation if the SCSI device initiates it. If neither the host adapter nor the SCSI
device initiates synchronous 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.
l
Maximum Sync Transfer Rate — Sets the maximum synchronous data transfer rate that the host adapter supports. The AHA-7899 host
adapter supports rates up to 160 megabytes per second (MB/sec), and the AHA-7880 host adapter supports rates up to 40 MB/sec. The
default setting for the AHA-7899 is 160 MB/sec (its maximum). The default setting for the AHA-7880 is 20 MB/sec.
If the host adapter is set to not negotiate for synchronous data transfer, the maximum synchronous transfer rate is the maximum rate
that the host adapter accepts from the device during negotiation. (This is standard SCSI protocol.)
l Enable Disconnection (sometimes called disconnect/reconnect) — Determines whether the host adapter allows the SCSI device to
disconnect from the SCSI bus. 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.
Leave Enable Disconnection set to Yes if two or more SCSI devices are connected to the host adapter. This optimizes SCSI bus
performance. If only one SCSI device is connected to the host adapter, set Enable Disconnection to No to achieve slightly better
performance.
l Initiate Wide Negotiation — Determines whether the host adapter attempts 16-bit data transfer instead of 8-bit data transfer. The default
setting is Yes.
When this option is set to Yes, the host adapter attempts 16-bit transfer. When this option is 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.
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Send Start Unit Command — Determines whether the start unit command is sent to the SCSI device during the boot routine. The default
setting is Yes.
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 this option is 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.
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BIOS Multiple LUN Support — Provides support for peripherals that contain multiple SCSI devices, such as autoloading tape drives and
CD-ROM changers.
l Include in BIOS Scan — Enables you to set whether the system BIOS scans this device during system start-up. The default setting is Yes.
Advanced Host Adapter Settings
The advanced host adapter settings should not be changed unless absolutely necessary. These values are set by Dell, and changing them may
cause conflicts with the SCSI devices.
l Host Adapter BIOS — Enables or disables the host adapter BIOS. The default setting is Enabled.
If you are booting from a SCSI hard-disk drive connected to the host adapter, the BIOS must be enabled. You should disable the host
adapter BIOS if the peripherals on the SCSI bus (for example, CD-ROM drives) are all controlled by device drivers and do not need the
BIOS.
l Support Removable Disks Under BIOS As Fixed Disks — Controls which removable-media drives are supported by the host adapter
BIOS. The default setting is Boot Only. The following choices are available.
NOTICE: If a removable-media SCSI device is controlled by the host adapter BIOS, do not remove the media while the drive is on or
you may lose data. If you want to be able to remove media while the drive is on, install your removable-media device driver and set
this option to Disabled.
l Boot Only — Only the removable-media drive designated as the boot device is treated as a hard-disk drive.
NOTE: Some older SCSI-1 devices do not support synchronous 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.
NOTE: Some 8-bit SCSI devices may have trouble handling wide negotiation, which may result in erratic behavior or a hang
condition. For these devices, set Initiate Wide Negotiation to No.
NOTE: For many devices, if Send Start Unit Command is set to Yes, the boot routine time will vary depending on how long it
takes each drive to start.
NOTE: Several SCSISelect options are not valid unless the host adapter BIOS is enabled.