20 Oct
2005
20 Oct
'05
11:18 a.m.
Chuck Guzis wrote:
On 10/20/2005 at 5:48 PM Jules Richardson wrote:
Brilliant - most informative, thanks :) (although I've seen mention of
the hack-like nature of the cable twist on this list before, I don't
remember anyone ever saying why it was done!)
That does beg the question of whether there's any other jumpering to
worry about when putting a PC-setup floppy onto a classic system (other
than getting the drive select jumpering right).
cheers
Jules
... discussion about this on another list got me
curious - what *was*
the point of that cable twist in a (IBM clone) PC floppy cable, when
every other system on the planet was using straight-through cables?
It's actually pretty simple--there's only a single "motor on" line for
the
standard floppy pinout. IBM wanted to control drive motors individually.
The only ways to do that are with individual drive cables or using the
"twist" (or some modification of it) so that the individual drive motor
enables are given different conductors in the cable.