Subject: Re: New to the club...
To: Brian Hechinger <>
From: None <>
List: port-sparc
Date: 06/18/2001 22:53:51

> On Mon, Jun 18, 2001 at 03:58:07PM -0400, Greg A. Woods wrote:
> > > I definitely don't think putting a longer cable with a second 
> > > hard drive on it is within the specs.
> > Indeed it's not.
> ah, but "within the spec" and "magically still works" are two entirely
> different things. :)

But then 'magically works' is not quite what I would want. I had my share in
magic when I had to repair 5GHz radio equipment in military service. And
yes, a SCSI connection (as opposed to EIDE) is a HF bus, not just a connector. 

That's why we have the termination and the other restrictions on the specs.
The 15cm minimum distance between devices is defined, so that half a wave
will fit in between and the 10cm maximum length of a stub is below, so that the
half wave doesn't fit. 

If you don't obey to these rules you introduce reflections on your bus. For
that matter any stub causes reflections, so even the Sun way of doing things
is stretching the limits already. If you have reflections on your bus you
might be lucky that they eliminate themselves or not so lucky because they
amplify themselves depending on the rest of your configuration.

To make a long speach short: Be prepared for your disks to stop working when
you f.e. add an external device. It's pure luck.