14 Feb
2002
14 Feb
'02
11:24 a.m.
Actually, in the current "standard" for IBM-style implementation of the FD
cable, there is a 3rd drive select. The fact that the selects aren't used in
the normal way is no surprise, but the result is that you can have 2 floppy
drives and a tape drive, but you can't use the floppy drives while you are
running the tape drive because there's no telling who uses that 3rd select
signal for something else.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, February 14, 2002 3:12 PM
Subject: Re: Drive inventory
On Thu, 14 Feb 2002, Tothwolf wrote:
Actually they _have_ to break the rules. If they followed the rules,
they'd appear as a floppy drive, and you'd be limited to the tape drive
and one floppy drive on the cable. Most people want(ed?) to have 2 floppy
drives + the tape drive, so the tape drive has to break the rules for
drive selection. It can't simply use one of the drive select lines.
-tony
That would work well if all the tape drives that
use the floppy
interface followed the rules, but not all do. I guess it would be
possible to build a board with some logic chips that could isolate
individual drives from the bus, but I think it would be much easier for
now to only connect one drive at a time.
Can you elucidate? How can a floppy interface tape drive not follow the
rules and still work?