bobgoodwin wrote:
Mike McCarty wrote:
bobgoodwin wrote:
[snip]
If you use M/S jumpering on the drives, then in theory it doesn't matter
where you connect them.
Except it appears to me that it matters as far as terminating the line
properly is concerned. Ideally it would seem the termination should be
at the far end where the master is connected to avoid the possibility of
a mismatch at the end of the stub that would result if the slave is at
the far end. How much ringing might occur and the severity of it's
effect is an unknown? It would be interesting if I could get into the
circuit and poke around with a scope probe ...
Agreed.
[snip]
I thought "cable select" cables had wires obviously crossed in the
ribbon cable but that may not be true with this 80 wire ribbon?
Not crossed. For CS, the drives have resistive pull-ups on them. The MB
pulls down one line. The wire to this line is *severed* as the slave
connector, so the "master" sees a high, while the "slave" sees
a low on this pin. (The MB may have a pull-up and the drives
a pull-down, I forget the polarity.)
If the h/d manufacturer provided this explanation this thread would
never have started. I would have never asked any questions. It appears
Well, just how much of the interface should they document? Each pin?
Just the Cable Select pin?
that I probably have cable select which I will try here in a little
while. The drives can be jumpered for CS and I have 80 wire ribbon
cables so it appears that should work if I understand everything I've
read here? It would be helpful if the user knew that he was dealing
with a c/s cable, there is no mark apparently other than the fact that
there are more wires than connector pins to tie them to?
Color of the connectors. Usually non-CS cables use just one color
of connector, presumably because they can get better volume
prices that way. CS cables are supposed to use blue for the MB
connector, black for "master" and grey for "slave", IIRC.
Mike
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