Setting up a SCSI chain

The first step is simple enough. Install the SCSI card. Most cards today are plug and play and Windows will find and configure them quickly and easily. The next step is to cable the devices together and set the I.D.s and termination (if necessary). Each device on a SCSI chain requires its own I.D.

 

 

 

As an example (example is an 8 device chain):

ID#0 – hard drive
ID#1 – CD-ROM
ID#2 – CD-R
ID#3 – Internal Jaz
ID#4 – Scanner
ID#5 – Hard drive
ID#6 – Zip
ID#7 – SCSI Card

 

If two devices are set to have the same I.D., the whole chain may not work, or possibly just the conflicting devices. ALWAYS make sure each device has a different I.D. Most devices have jumpers or a small dial for setting the I.D. number. The hard drive at ID#0 should be your boot drive (if you are booting SCSI), and the CD-ROM is set at the lowest available I.D.# in order to have it assigned a drive letter before the CD-R.

Terminate it

Termination is a separate issue, but it also affects your SCSI bus a great deal. Each device at the far ends of a SCSI chain must be terminated. This refers to their physical location on the chain and NOT their ID number. In the above example, the scanner is probably at one end of the chain, and possibly a hard drive is at the other, with the card in the middle, like so:

Scanner
ZIP
Card
CD-ROM
CD-R
Jaz
Hard drive
Hard drive

So, unless the devices are auto-terminating, that hard drive and the scanner must be set to terminate, usually by jumpers or a switch on the device. In older devices, this might actually require placing a terminator on the end of the chain. Generally, that is no longer necessary. All items between the ends must have their termination disabled, or the chain will not operate properly. If you have all internal devices or all external devices, then the card itself will be an end device and must be terminated. If you have a couple of auto termination devices, and a few which are not, you can try to set the auto termination devices at the ends of the chain to make setup easier.

SCSI Troubleshooting Tips

Despite the reputation of being difficult to configure, I have found that SCSI is extremely easy to get up and running. Pay attention to the issues above and you should be fine. Just in case, here are a few troubleshooting tips:

 

  • Check Termination First. Then check it again.
  • Check I.D.#s
  • Use quality cables. If you have a problem, especially with a fast hard drive, try changing the cable.
  • Use the shortest connections possible. Pay attention to the maximum total length.
  • Make sure you have the newest ASPI drivers (Adaptec site if you have an Adaptec card).
  • Make sure the cables are plugged in correctly and firmly: pin 1 to pin 1.
  • If you are not sure your devices are SCAM compliant, turn it off.
  • Check for IRQ conflicts.

Page 1: Introduction to SCSI
Page 2: Choosing SCSI devices
Page 3: This page: Setting up a SCSI chain

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