[SunRescue] Re: ObQuestion

[Robert Rose]

>
>From: "Loomis, Rip" <GILBERT.R.LOOMIS at saic.com>
>
>ObQuestion:
>I've never played with differential SCSI-2 before,
>but I've just been handed an SBus wide differential
>plus Ethernet card.  Any things I should know about
>cabling/termination differences between this and
>regular FW/SE SCSI?

Yep, there are similarities and differences.  As long as you use wide or 
narrow cables, there is no effective difference between Differential and 
Single Ended, they're wired "straight through".  There is a difference in 
length, differential can be *heaps* longer than SE.

SCA throws an interesting twist, there are differences between SE and Diff 
such that a regular (SE) SCA to 50/68 pin adaptor isn't supposed to work 
with a Diff SCA disk and controller.  There are Diff specific SCA to 50/68 
pin adaptors priced at a premium above the SE variants, probably because 
they're less popular.  Hands up if you've ever used a Diff SCA disk..... 
not many I bet.  I didn't even know such a beastie existed 'till I picked 
some up at auction.  Seagate don't even acknowledge they exist on their 
website.

Termination is different between SE and Diff, they're not 
interchangable.  The Seagate drives I've seen (narrow, wide and SCA) don't 
even have an option of termination like the SE drives do, so you're stuck 
trying to find an external one.

Does anyone that's bothered to read this far know where I can find a cheap 
68 pin Diff SCSI terminator?  I've got the drives, I've got the controller, 
I just need to terminate the damn bus.  I've got a 50 pin terminator, but 
I'd really like to get the whole bus running Wide instead of narrow.

cheers,

Rob.