Installing and configuring a SCSI tape drive is a bit more complicated than installing an ATAPI model. Rather than attempting to provide step-by-step instructions, which vary according to the specific drive and adapter, we've chosen to illustrate a typical installation using a Seagate Hornet NS20 drive and an Adaptec 2930 SCSI host adapter, both representative selections.

• If you have not already done so, install the SCSI host adapter. To do so, power down the system, remove the cover, and locate an available bus-mastering PCI slot. (Some older systems don't support bus mastering on all slots. Bus-mastering slots are usually white or ivory; non-bus-mastering slots are brown or black.) Remove the slot cover for the selected slot, align the bus connector with the slot, and press down firmly to seat the adapter. Use the screw that secured the slot cover to secure the adapter. If you have a spare drive activity indicator LED, connect it to J2 on the host adapter to indicate SCSI bus activity.

• The Adaptec host adapter supports SCAM (SCSI Configured Auto-Magically)—a kind of Plug and Play for SCSI that automatically configures SCSI ID and termination. Like most tape drives, the Seagate Travan NS20 does not support SCAM, so we'll have to set jumpers manually to assign SCSI ID and set termination.

  Like most manually configured SCSI devices, the Seagate Travan NS20 drive has three jumpers—ID0 (SCSI ID 1), ID1 (SCSI ID 2), and ID2 (SCSI ID 4). Installing jumper blocks on zero or more of these jumpers allows you to set SCSI IDs 0 through 7. Connecting no jumpers assigns SCSI ID 0. Connecting one jumper assigns the SCSI ID associated with that jumper (e.g., ID1 assigns SCSI ID 2). Connecting two jumpers assigns the SCSI ID that is the sum of the two jumpers (e.g., ID0 and ID2 sums the SCSI IDs 1 and 4 to assign the SCSI ID 5). Connecting all three jumpers assigns SCSI ID 7. Like most SCSI tape drives that require the SCSI ID to be assigned manually, the Seagate Travan NS20 drive by default is jumpered to SCSI ID 4, which is usually not in use by other devices.

  Avoid setting a tape drive to SCSI ID 0, 1, or 7. ID 0 is reserved by convention for a bootable hard drive, ID 1 for a second hard drive, and ID 7 for the host adapter.

• The Seagate Travan NS20 drive also requires setting termination manually. Exactly two devices must be terminated on each SCSI bus, and these devices must be those at each end of the bus, as follows:

  • 1. If the SCSI adapter has only internal devices attached to it, the adapter itself and the final device on the internal SCSI chain must be terminated.

  • 2. If the SCSI adapter has only external devices attached to it, the adapter itself and the final device on the external SCSI chain must be terminated.

  • 3. If the SCSI adapter has both internal and external devices attached to it, the adapter must not be terminated. Instead, terminate the final internal device and the final external device attached to the SCSI chain

In this case, the Seagate tape drive is the final device on the internal SCSI chain, which has no external devices, so the drive and the host adapter must both be terminated. By default, Pins 3 and 4 on the drive are jumpered, which terminates it. That's the correct setting, so we leave it as is. If we were installing the Seagate Travan NS20 between two existing SCSI devices, we'd remove the jumper from Pins 3 and 4 to disable termination.

Pins 1 and 2 are also jumpered by default, which enables Termination Power. Again, that's the correct setting, so we leave it at default. Pins 5/6 and 7/8 are reserved on this drive, so we leave them unjumpered, which is the default. Pins 9/10 are jumpered, which enables Parity Checking. Again, that's the correct setting, so we leave it at default.

Most drives ship with Termination Power and Parity Checking enabled, which is usually correct. If you have trouble accessing a tape drive, check the host adapter manual to determine if Termination Power and/or Parity Checking should be disabled.

Adaptec host adapters, which we use and recommend exclusively, by default automatically detect terminated SCSI devices on the bus and set their own termination status accordingly, so no further action is required to configure the drive properly. Note that a few internal SCSI cables have a built-in terminator at the end of the cable. If you use such a cable, make sure that termination is disabled on all drives connected to that cable.

• Once you have resolved SCSI ID and termination issues and have the drive physically installed, the next step is to connect the cables. Most adapters are supplied with a standard two-device cable. If you need to connect more than two drives, replace the cable before proceeding. Otherwise, connect the cable to each drive, making sure to align Pin 1 on the cable (indicated by a red stripe) with Pin 1 on each device (indicated by a small number, triangle, or dot on the connector). For SCSI IDs, it doesn't matter which drive connects to which cable position, so mix and match drives and cable positions in whatever way makes it easiest to route the cable. Just make sure that the physical last drive on the cable is the one that's terminated. Connect the power cable.

• After verifying all settings and connections, turn on any external SCSI device(s) first, and then turn on the PC. Ordinarily, the system should boot normally, but the SCSI tape drive may or may not be recognized, depending on the drive itself, your operating system, and other factors. Before you configure the operating system to use the drive, some systems may require one or both of the following steps:

  CMOS Setup

  On most systems, the PCI bus assigns IRQs and port addresses automatically. If your system requires setting PCI bus parameters manually, do so during the first restart, using the system or motherboard documentation for guidance. (If your system BIOS is capable of assigning IRQs automatically, there will usually be a CMOS Setup option worded something like "Plug and Play OS?" If that option is set to No, the PC BIOS assigns IRQs. If it is set to Yes, the BIOS allows the Plug and Play capable OS [Windows 9X/2000/XP/Linux] to assign IRQs).

  SCSI Setup

  At boot time, the SCSI BIOS displays adapter and BIOS information and a list of installed SCSI devices. Ordinarily, the default settings are fine, but in some cases you may need to change settings to get the drive to work at all or to optimize its performance. If this is the case for your system, press whatever key sequence is needed to invoke the SCSI Setup routine and make the necessary changes, as recommended by the documentation for the host adapter and/or drive.

  If either or both of these steps are needed, restart the system after completing each. After you complete these steps, the system should boot normally and physically recognize the tape drive.