Hard drive cable question -

[bobgoodwin]

Mike McCarty wrote:

> bobgoodwin wrote:
>
>>
>> Does it matter which forty pin connector plugs into the master and 
>> slave drives?
>> I have come to the realization after struggling with some problems 
>> that there are a lot more wires in the ribbon cable than there are 
>> connector pins.
>
>
> If you have more wires than pins, you almost surely have a CABLE SELECT
> cable. In fact, if your cable is less than five years old, you probably
> have CS. Which end goes where depends on how you jumper your hard
> drives.
>
>> I now see that Maxtor designates the connector at the end of the 
>> cable as the "master" and the one just below it as the "slave."  I 
>> presently have only one drive jumpered as master with FC4 running on 
>> it and it 
>
>
> 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 ...

>
>> ;doesn't seem to care which data cable connector is attached to it, 
>> but when I put in the second drive, jumpered as "slave" the computer 
>> won't boot.  I decided the drive was bad but now I'm wondering? It 
>> may be the wrong connectors plugged into the drives.
>>
>> 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 
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?

> Floppies have a "twist" in their cables, not hard drives.
>
>> Can someone clear this up for me.
>
>
> HTH
>
> Mike