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Please pay attention to the following operations when connecting multiple SCSI devices:

 Narrow (50pin) SCSI controller can make a daisy chain to seven extra SCSI devices. Counting the

controller, there are eight SCSI devices totally.

 Wide (68pin) SCSI controller can make a daisy chain to fifteen extra SCSI devices. There are sixteen

SCSI devices totally through counting the controller.

If connect the two Narrow (50pin) SCSI controllers to SCSI interface on separate system board, each controller

may connect with seven SCSI devices. There are sixteen SCSI devices totally through counting the controller.

We suggest you that not use SCSI devices in different width on the same SCSI chain or the same SCSI channel,

otherwise the data transfer rate will get slow. The only exception is when connecting SCSI device in super-width

to other 68pin device, it will slow down the speed of detection and repair.

If the multiple devices are used, the device will be separated between Channel A and B. The length of cable on

the second channel should not exceed 18 inch.

If you want to use two controllers, each controller is able to use the SCSI device in different width and speed. To

connect a 68pin data line with 50pin SCSI device controller, you need to adopt built-in cable adapter or external

cable adapter.

All SCSI controllers must allocate unique SCSI ID (0-7 or 8-15) to SCSI devices installed. The controller identifies

the SCSI device according to SCSI ID (not SCSI device address). The communication between controller and SCSI

device will not be affected by transferring SCSI device from one position to another position on SCSI chain.

Open all external SCSI devices before turning the power on, and SCSI controller enabled can identify the external

devices.

4.2.2 Jumper Notices

Configure drive options

For option jumper locations and definitions refer to Figures 1, 2, and 3. Drive default mode parameters are not

normally needed for installation.

• Ensure that the SCSI ID of the drive is not the same as the host adapter. Most host adapters use SCSI ID 7

because ID 7 is the highest priority on both 8 and 16 bit data buses.

• If multiple devices are on the bus set the drive SCSI ID to one that is not presently used by other devices on the

bus.

• If the drive is the only device on the bus, attach it to the end of the SCSI bus cable. The user, system integrator,

or host equipment manufacturer must provide external terminators.

Drive ID/option select header

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Seagate ST39251LC Manuale Utente Pagina 29