Subject: Re: Dual SCSI, single chain?
To: Curt Sampson <>
From: Wilko Bulte <>
List: port-alpha
Date: 03/29/1999 19:32:17
As Curt Sampson wrote ...
> On Sun, 28 Mar 1999, Greg A. Woods wrote:
> > Also, unless you're using full differential, or LVD, there are many
> > restrictions on the mixing of "slow", "fast", and "ultra-fast" devices
> > on the same bus...
> No, this is certainly not the case. You can mix any combination of
> stuff you want (excepting differential)--narrow, wide, slow, fast,
> ultra, etc., so long as you don't mind the bus contention (i.e.,
> a 4 MHz CD-ROM drive transferring 1 MB/sec is going to use a quarter
> of the bus bandwidth regardless of the width and speed of the
> controller and other devices on the bus). In fact, LVD is the only
> one you can't mix without losing capabilities (LVD devices revert
> to single-ended if there are any non-LVD devices on the bus), and
> differential is the only one you can't mix at all.

This is the theory alright. Unfortunately the older devices 
can cause troubles when connected to faster/newer buses. Things like
bus stubs etc come to mind. The older devices were built in times
when the electrical characteristics were not so important.

But again, there are lots of people who do it and have it working. I do.
But when it stops working I generally know how to fix it: seperating old
& new worlds often helps.

Groeten / Cheers,
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