to terminate or not to terminate

[Christopher Caldwell]

According to the Reponse Center, the A5150A SCSI card is self terminating. The A4800A is not. It depends on who you ask, but some seem to think that the A4800A requires an external terminator if _no_ devices are hung from the bus (we've removed the attached storage). I'm interested in practical experience wrt terminating SCSI cards with no devices attached ... given that the bus isn't terminated, does the box tank? Do things become unusable, or is it business as usual given that the bus isn't in use from an equipment perspective.

[Michael Tully · Accepted solution]

Hi Chris,

I've this card a few times in different servers, and have only terminated it (A4800A) when there has been devices attached, i.e. a tape drive. I was always of the belief that this card was self-terminating, if nothing was attached.

Regards
Michael

[Thomas Bianco]

One of our Unix admins would disagree with me, but normally there is no need to connect an external terminator if there are no external devices. I have never had a server fail due to a bus being unterminated on the side without any devices on it.

As I mentioned above, my Unix admin would disagree, saying that it's safer to terminate the bus regardless. Heâ s never had a server fail because it's been double terminated.

Usually, when a bus is unterminated, the card will not see any devices. This is largely due to the fact that there is no real noise filtration on digital signal cards like SCSI, and echoes on an unterminated bus can be as loud then the signa

[Christopher Caldwell]

We tested this out by removing the cables without adding terminators. We didn't encounter any problems.