23 Mar
2010
23 Mar
'10
8:06 p.m.
Is this likely
to work? I realise I'll need to find drives with a unit
selection jumper on them, so I can set one as 0 and the other as 1; no
twists in the cables this far back, & I'm guessing that a twisted
cable wouldn't work with a controller that wasn't expecting it...?
Why not? The whole reason for the twisted cable was so that when
controller would send signals to drives 0 and 1, the correct drive would
respons, in spite of both drives being jumpered as "B:". from the drive selects alone and moves the drive select
signals around so
that each drive select output of the cotroller ends up on the
'active'
drive select signal (normally DS1/ for a PC drive) of a differnt drive.
WHY did they do it that way? One reason was so that
users, and
"technicians" at Computerland, etc., would not need to figure out and
understand jumpers.
I am not convinced that was the real reason. After all, with the 5.25"
full-height drives in the PC you had to fit a terminating ressitor
package to the last drive on the cable (And yes, IBM did get that right).
Anyone who could fit/remove resstor packs correctly could set jumpers.
I still think the real reason was to have separate motor-on signals for
the 2 drvies. The fact that it allowed all drives to be strapped the same
way is a bonus.
-tony