Terminating SCSI chain - Squizzle

[Cyberus]

I saw someone selling a Squirrel SCSI and external CDROM on ebay. There is no SCSI terminator included in the auction, and I emailed the guy and asked him about it, and he said it didn't need one. But I thought you had to terminate a SCSI chain, even if its just one device? So is it possible the CDROM (originally sold by Power bundled with the Squirrel) is self terminating?

Oh the motivation for asking this is academic as much as anything, as I don't intend to buy the Squirrel - I have one here but no working A1200 to use it with.

Cheers

[SilvrDrgn]

Yes, it is possible that the CD-ROM drive is self-terminating.

[shaf]

The CD-ROM probably has it's termination block enabled. All SCSI I and SCSI II devices allow termination to be enabled on every device. It's only when you go to SCSI III 68 and 80 Pin Connectors that the Termination is done o the cable and there is no allowance to terminate the device.

Shaf

[Ilwrath]

Most likely, the CD-ROM has it's own termination set.  The Squirrel A1200 card isn't a super speedster, but it's very tolerant of SCSI errors and noise.  Mine ran great, no matter what I threw on the chain, so long as I kept the card cool.  I wish I hadn't sold it ages ago.  

[Lo]

But I thought you had to terminate a SCSI chain, even if its just one device?

So did I, but my A3001 GVP_030*50 had a HDD mounted vertically on the accelerator itself, the data cable was so short, GVP told me it did not need termination.  :-?

[ShawnD]

the data cable was so short, GVP told me it did not need termination.

That makes sense since termination takes care of 'reflections' off the ends of the cable.  On a short cable the reflectiosn aren't nearly as bad.  

However on SCSI I though the terminator also was used to keep the bus from floating when no-one was using it.  This suggests that there should always be at least one terminator.

[iamaboringperson]

-You should have a terminator at either end of the chain
-Many devices include built in terminators
-It is possible to use devices even when the chain is incorrectly terminated, including no termination at all. The main problem that I have found with an incorrectly terminated SCSI chain was that it was slow, I also found that a drive wouldn't complete reading and writting under windows until I tried to access another file.