Settle a dispute over SCSI termination

[Tsaico]

Help me out guys, I have a dinner riding on this one, so here goes:
SCSI setup is as follows,
ID #
1- Yamaha 8x8x24
6-35x Plextor
7- SCSI adapter (it has a termination option)

So the question is where are the termination points?

 

[Moohooya]

SCSI must be terminated at the two ends of the cable. The device id has no relevance. Any device can have any id, including the controller. I believe the id is tied to a priority order, but I doubt many people need to change them.

You can put any device, including the controller, anywhere on the cable. Typically people put the controller at an end as that has a built in terminator. Older devices don't have terminators, but more and more devices these days do. There are two types of terminators. Active and passive. The difference is an active terminator uses a small voltage regulator and ties all the lines to that voltage via resistors. Passive terminators just use resistors to the +5v and ground. As the +5v may not be +5v at the end of the cable, the termination is not as good as the active.

You can buy terminators seperatly. Typically they are very expensive for what they are. ($20-$30) I did find and buy one for under $10 a few years ago, but it took time to find one for that price. I'm guessing SCSI drive manufactorers are including terminators on the drives more and more now to simplify and reduce the cost of a SCSI system. I think there may even be auto termination out there, but if someone said that was a load of BS, believe them not me.

So, look to see which device is at the end and check it has either a built in terminator that is either enabled or automatic, or an external one.

 

[datallah]

Well... there is not enough information there to fully answer that question.

The termination doesn't have anything to do with which SCSI IDs devices are using. Rather, it has to do with their position on the cable.

The devices connected to both ends of the SCSI channel need to be terminated (the SCSI card will almost always terminate itself unless you are using both external and internal devices on the same channel). So... assuming both are internal drives on the same cable, the termination points will be (a) SCSI Adaptor (b) Drive farthest from SCSI card on cable.

Thank you and goodnight.

 

[datallah]

Haha.. some1 beat me to it...

Also, i know for a fact that both of those drives have built-in termination via a jumper.

 

[Woodie]

Not relevant for the original poster, but...

LVD drives do not have a termination option (they may, but it won't properly terminate an LVD chain).

At least that's what I was told.

--Woodie

 

[datallah]

Woodie... That is true.. That is why internal LVD cables have a built-in active terminator at one end.

 

[MereMortal]

<<Any device can have any id, including the controller.>>

For LVD controllers, this is not true. 8-bit devices must have ID's in the range 0-6, since these drives only have 3 jumpers (0-8), not 4 (0-15).

 

[Hoholi]

<< Help me out guys, I have a dinner riding on this one, so here goes:
SCSI setup is as follows,
ID #
1- Yamaha 8x8x24
6-35x Plextor
7- SCSI adapter (it has a termination option)

So the question is where are the termination points? >>



On the back off the drives are several jumpers; some are used for SCSI ID (4) Normally you don't have to alter them; you have only be sure that each device has a DIFFERENT id. there is also one jumper that controlls the termination : factory standard they are probably ENABELD sho you have to look on the devices or more easyli in your manual. Since only the LAST device in a scsi chain must have termination ON you have to check them. For instance if your last device is the Yamaha (= last device on the chain/cable) then the Yamaha must have termination ON and the Plextor OFF. (OFF = remove jumper) The termination on the adapter is on most off the cards set to AUTOMATIC but can often be alterd in a bios (for booting devices). Active termination is not needed and more expensive if you have not that much devices or if the Scsi chain is not to long. There is more to win in using good quality cables than with active termination.

 

[Hoholi]

<< Help me out guys, I have a dinner riding on this one, so here goes:
SCSI setup is as follows,
ID #
1- Yamaha 8x8x24
6-35x Plextor
7- SCSI adapter (it has a termination option)

So the question is where are the termination points? >>



On the back off the drives are several jumpers; some are used for SCSI ID (4) Normally you don't have to alter them; you have only be sure that each device has a DIFFERENT id. there is also one jumper that controlls the termination : factory standard they are probably ENABELD sho you have to look on the devices or more easyli in your manual. Since only the LAST device in a scsi chain must have termination ON you have to check them. For instance if your last device is the Yamaha (= last device on the chain/cable) then the Yamaha must have termination ON and the Plextor OFF. (OFF = remove jumper) The termination on the adapter is on most off the cards set to AUTOMATIC but can often be alterd in a bios (for booting devices). Active termination is not needed and more expensive if you have not that much devices or if the Scsi chain is not to long. There is more to win in using good quality cables than with active termination.

 

[Tsaico]

Cool! Now my next question for you guys is where I should be asking for my free dinner... And sorry, I presumed that most people usually go in ascending or descending order, starting at the end of the cable, with boot drives at 0 on the end and usually the card at 7. But hey, if not, oh well, Assuming makes an ass out u and me.... Thanks again...