On Thursday 23 February 2006 21:35, Gene Heskett wrote:
On Thursday 23 February 2006 16:18, Mike McCarty wrote:
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.
And someone else quoted the last two in reverse. Can someone PLEASE go get one of these friggin cables and settle the argument? Good color vision required of course :)
Ok I just took the place apart, and the only two cables I have that MIGHT be CS cables came with an original promise 20267 raid card that I was going to use at one time for a raid here. Those two cables are blue for the card end and its keyed too, grey for the (s/b slave) next, and black for the end (s/b master) one. But I gave that up when the horror stories about the 20267 started surfaceing on lkml. I don't know if all its bugs have been coded around now or not.
Mike
p="p=%c%s%c;main(){printf(p,34,p,34);}";main(){printf(p,34,p,34);} This message made from 100% recycled bits. You have found the bank of Larn. I can explain it for you, but I can't understand it for you. I speak only for myself, and I am unanimous in that!
-- Cheers, Gene People having trouble with vz bouncing email to me should add the word 'online' between the 'verizon', and the dot which bypasses vz's stupid bounce rules. I do use spamassassin too. :-) Yahoo.com and AOL/TW attorneys please note, additions to the above message by Gene Heskett are: Copyright 2006 by Maurice Eugene Heskett, all rights reserved.