A very brief trouble shooting guide for Small
Computer System Interface (SCSI) adapters:
- Make sure you are using the latest BIOS from your
motherboard manufacturer. Some have had problems with their PCI bus slots not working
- Check to be sure that all SCSI devices attached to the bus
- Make sure all SCSI cables and power cables properly
connected. Try removing and reseating all the connectors to be sure.
- Check that the host adapter and each device on each SCSI
bus channel have a unique SCSI ID setting.
- Make sure the SCSI bus is terminated properly. Remember
there should only be two terminators on the bus, one on each end. All other termination
should be removed or disabled.
- If your system BIOS setup has settings for controlling PCI
bus configuration, make sure the PCI slot containing the SCSI adapter is configured for an
available interrupt. If your system is Plug and Play, use the Windows Device Manager to
check and possibly change the resource configuration.
- Make sure the host adapter is installed in a PCI slot that
supports bus mastering. Check your motherboard documentation and try moving the SCSI host
adapter to a different PCI slot.
Some additional tips:
- Start by adding one device at a time. Rather than plug
numerous peripherals into a single card all at once, start with the host adapter. Then
install one device, making sure everything works before moving on to the next.
- Keep good documentation. When you add a Device, write down
the SCSI ID address, any other switch and jumper settings, such as SCSI Parity, Terminator
power and Delayed or Remote Start. For the host adapter, record the BIOS addresses,
Interrupt, DMA channel and I/O Port addresses used by the adapter and any other jumper or
configuration settings, such as termination, that might be important to know later.
- Use proper termination. Each end of the bus must be
terminated, preferably with active or Forced Perfect,FPT terminators. If you are using any
Fast SCSI-2 device, you must use active terminators rather than the cheaper passive types.
If you have only internal or external devices on the bus, the host adapter and last device
on the chain should be terminated. If you have external and internal devices on the chain,
you generally will terminate the first and last of these devices but not the SCSI host
adapter, which is in the middle of the bus.
- Use high-quality shielded SCSI cables. Make sure that your
cable connectors match your devices.
The SCSI ID setting is very simple. Up to 7 SCSI devices
can be used on a single narrow SCSI bus or up to 15 devices on a wide SCSI bus. Each
device must have its own unique SCSI ID address. There are 8 or 16 addresses respectively
and the host adapters are factory set to ID7 or 15, which is the highest priority ID.
SCSI termination is required at both ends of the bus,
there are no exceptions. If the host adapter is at one end of the bus it must have
termination enabled. If the host adapter is in the middle of the bus, and if both internal
and external bus links are present, the host adapter must have termination disabled and
the devices at each end of the bus must have terminators installed.
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