Q: Can I connect older style 50-pin narrow SE = single-ended SCSI devices (such as a DAT drive) to my wide-SCSI bus? With what adapters or cables?
A: Yes. Systems with internal CD-ROM or tape drives use a 68-pin female to 50-pin male (wide SCSI to narrow SCSI) adapter. Take a look to see ifyou have any systems with a CD-ROM drive. The only caveat with such an adapter is handling termination.
If the narrow (50-pin) device is at the end of the SCSI chain, you need a special adapter that terminates the unused pins. To avoid this problem, put your wide-SCSI hard disk drive(s) at the end of the internal SCSI chain, so that the chain is terminated on a wide-SCSI device. You can then add narrow devices using the wide-to-narrow adapter in the middle of the chain without worrying about termination; they are not terminated.
To connect external narrow devices, you have the same worry about termination: You will want to acquire an external wide-to-narrow adapter that correctly terminates the unused pins. Most wide-to-narrow adapters don`t handle this correctly. Many problems are caused by people trying to use improperly terminated external narrow-SCSI devices. Your adapter (for such an external device) should be one that terminates the high-order bits.
 March 2001 revision: This is not true on systems containing internal-only SCSI chains. If you have such a system, you might be tempted to extend one of the internal chains to reach external SCSI devices, but please be aware that omission of an external connector probably means the manufacturer has not qualified such hardware configurations, and they may malfunction (e.g., by exceeding SCSI chain-length, device-spacing, or other cabling specifications). Generally, it's wiser in such cases to purchase an additional SCSI host adapter possessing an external connector, to service any external devices.