"James Stanley: SGI-Zone Admin." writes:

> Hello all,
>
> I have a question about the difference between differential SCSI and
> 'regular' SCSI. What is it? I am working on a Challenge Vault M and the
> owner manual makes a big deal about it being differential or not. I am
> looking to connect it to my Challenge M but the manual says that it will
> not work. From looking at all the cabling and connections the only thing
> I see that might be different is the drives themselves.

www.scsifaq.org

*p

In article ,
James Stanley: SGI-Zone Admin. wrote:

>Hello all,

> I have a question about the difference between differential SCSI and
>'regular' SCSI. What is it? I am working on a Challenge Vault M and the
>owner manual makes a big deal about it being differential or not. I am
>looking to connect it to my Challenge M but the manual says that it will
>not work. From looking at all the cabling and connections the only thing
>I see that might be different is the drives themselves.

Differential drives use two signal lines that swing in opposite directions
to transfer each data signal (i.e., when D0+ goes high, D0- goes low, when
D0+ goes low, D0- goes high). This gives better noise immunity and allows
longer cable runs.

"Regular" SCSI is also called "single-ended"; with it, each data signal is
transfered by a single signal line referenced to ground. It's cheaper, but
doesn't give the same noise immunity or length of cable.

>Any help would be greatly appreciated,

They aren't interchangeable, and you can't use modern LVD drives in place
of old HDV drives. You can use LVD drives in place of single-ended drives,
may need to change a jumper.

You can probably modify your vault to use LVD drives in SE mode, but you'll
need a SE controller.

>Thanks in advance,


Gary

--
Gary Heston gheston@hiwaay.net

Contrary to popular opinion, _not_ everyone loves Raymond.