Pass-through active terminators

[Lemonty]

I was looking at PaSha's A4000T snapshots when I noticed he used these pass-through active terminators. See here (http://www.amiga.org/gallery/index.php?n=1091). I would normally use ordinary terminators which of course take up two connectors on the chain - you know, one at the beginning and one on the end. I am not sure how they work but is it fair to assume that they terminate the chain at the very end where they connect after they passed through the signal? That would be very handy. [Grumble mode on] Why doesn't the Cyberstorm have it's own terminator anyway? [Grumble mode off] Thank you.

[Thomas]

I am not sure how they work but is it fair to assume that they terminate the chain at the very end where they connect after they passed through the signal?


No. It is an adapter from 16bit to 8bit which terminates only the ending 8 bits. Usually you don't use it to connect a device but to connect a SCSI2 cable to the end of the SCSI3 cable.

If you connect it to a device, this device has to be the last one on the cable and has to have internal termination activated, too. Also the internal termination has to be active, not passive.

Usually SCSI2 drives only have passive termination, so what you are doing on the photo looks quite dangerous (unless you are sure the device has active internal termination).

I'd prefer to use real SCSI3 terminators at both ends of the cable and non-terminated adapters to connect SCSI2 devices.

Bye,
Thomas

[PaSha]

Lemonty wrote:
I was looking at PaSha's A4000T snapshots when I noticed he used these pass-through active terminators. See here (http://www.amiga.org/gallery/index.php?n=1091). I would normally use ordinary terminators which of course take up two connectors on the chain - you know, one at the beginning and one on the end. I am not sure how they work but is it fair to assume that they terminate the chain at the very end where they connect after they passed through the signal? That would be very handy.

Yup, that's how they work. Hence the 'passthrough'


[Grumble mode on] Why doesn't the Cyberstorm have it's own terminator anyway? [Grumble mode off] Thank you.
Probably due to lack of space on the PCB.

-Paul

[PaSha]

Thomas wrote:
No. It is an adapter from 16bit to 8bit which terminates only the ending 8 bits. Usually you don't use it to connect a device but to connect a SCSI2 cable to the end of the SCSI3 cable.

If you connect it to a device, this device has to be the last one on the cable and has to have internal termination activated, too. Also the internal termination has to be active, not passive.

Usually SCSI2 drives only have passive termination, so what you are doing on the photo looks quite dangerous (unless you are sure the device has active internal termination).

I'd prefer to use real SCSI3 terminators at both ends of the cable and non-terminated adapters to connect SCSI2 devices.

Bye,
Thomas

Not these.... the adapter on my CD-ROM drive is an unterminated 68-50 pin adapter, but the chunks on either end of my SCSI cable, are 68-pin UWSCSI (or SCSI3 if you prefer) Active passthrough terminators, terminating all 16 bits.

http://www.scsi4pc.com/scsi874.htm


[crappy ASCII drawing]
It basically works like this:

cable
|||||
terminator --- device
|||||
termination

[/crappy ASCII drawing]

So these are 'real SCSI3 terminators' and not 'dangerous' in any way... And looks way better than having loose terminators dangling off the ends of the cable.

quote from http://www.howtofixcomputers.com/bb/ftopic89771.html


A pass-through terminator is a terminator that allows you to put a terminator in a place where there is no connector left to put a standard one on.
The terminator is put on the device and then the cable is connected to that.
The SCSI specs allow this under the allowed stub length rules.


-Paul