The RF Spectrum On-Line

The Latest in Broadcast Technology - Fall, 1995

TECHNICALLY SPEAKING by Bob Owen

SCSI Checklist:

Here is a little help solving problems when installing or adding on to an existing SCSI bus in a PC-based digital automation system. In general, the steps to solving a SCSI problem are:

Is the host adapter being initialized? When the PC is booting, you should see a response on the screen that is from the SCSI host adapter. Look for error messages here. There may be an IRQ or memory address conflict between the adapter and something else in your system.
If the host adapter starts okay and you do have SCSI devices properly connected to the bus, you should see a response from those devices when the PC boots. If not, there are two likely candidates: improper ID or improper termination. Check the SCSI ID number of each device on the bus. Each device must have a different ID number. The host adapter is usually number 7. If you want to boot from a hard disk drive on the bus, the hard drive's ID must be number zero. The other devices on the bus can be any other number from 1 to 6, but each must be unique. The other likely possible problem is that the SCSI bus is not properly terminated. Termination resistors must be installed in the devices or on the cable, on both ends of the bus and not in the middle of the bus. Terminations can be either real resistor network packages or software controlled, so check the documentation of your particular SCSI device.
The final step is to check the software drivers. Whether you need them depends on the kind of device you are using. Generally, disk drives connect and work without extra software needing to be loaded. Most of the other SCSI devices require some extra software drivers. Refer to the installation programs that came with your CD-ROM and other devices.