From: William Levak (wlevak_at_sdf.lonestar.org)
Date: 2006-07-04 06:24:47
On Mon, 3 Jul 2006, Ethan Dicks wrote:
> What changed with PCs was the commercial expectation that people would
> only ever need up to 2 floppy drives per machine. The "magic twist"
> was a way of simplifying maintenance - flip the drive select part of
> the cable around and you won't ever have to restrap a floppy drive -
> just set it to DS1 (vs DS0) at the factory, and on a twist cable, it's
> positional - the drive before the twist is B: and the drive after the
> twist is A. The twist does, though, IIRC, prohibit a 4-drive cable.
> If the controller _would_ talk to 4 drives (some would, but not many),
> you could always make a straight cable with 5 connectors (controller
> and 4 drives) and set the drive jumpers. That ended with 3.5" drives,
> as most could only be selected to DS0 or DS1, then later, as
> manufacturing costs plummeted, they couldn't be selected at all
> without a soldering iron - they were DS1 and that's it.
The early PC's (PC, XT, AT) had provision for 4 floppy drives, 2 internal
and 2 external, on the same controller.
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