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11.1.3 Floppy Jumper
Die Jumper an Atari Floppy Laufwerken
Hier finden Sie alle relevanten Jumpersettings für die von
Atari verbauten Diskettenlaufwerke in allen Computertypen.
Here you found any jumper setting of all Atari relevant disc
drives.
The "twist" on some cables allows BOTH drives to be
physically set to Device 1. The "twisted" section reverses
the drive select lines so one drive responds as Device 0, even though
its jumpers are set for Device 1.
A standard PC type 3.5" disk drive use Pin 10 for drive
select 0 and Pin 12 for drive select 1.
The "twisted" section of cable on a PC floppy drive
cable is actually 6 wires wide- I'm not sure exactly why they reverse
that many wires, but for the Atari it may just be a matter of
reversing 10 and 12.
The reason IBM did this with the jumpers and twisted cables was
that back when they first introduced the IBM Personal Computer, most
systems were sold with only one floppy drive (and no hard drive)
because they were so expensive. Then when people discovered they
couldn't do much with a single floppy system, they would have the
second floppy drive added. As long as it was done by an
"official" IBM tech person, there was no problem.
But when people started buying the floppy drives by themselves and
trying to install them, the drives wouldn't work.
Rather than trying to explain to thousands of irate computer
owners how to change jumpers on their new floppy drives, IBM came up
with a way to allow ALL drives to be set the same, so no one ever had
to change the Device select jumpers. Because the normal situation was
someone trying to add a "B" drive, they started shipping ALL
floppy drives with the jumper set to "Device 1" , and
developed the twisted cable that allowed the drives to also respond as
Device 0 in the original installations.
Since the twisted cable became standard, the jumpers on the drives
themselves were superfluous and as you've seen, have finally been
removed from most designs available today.
In answer to some question about internal solder pad jumpers,
there's no real way to tell if they're present or not without the data
sheet (or taking the drive apart). I don't know just how common they
are, or indeed if there are drives that don't have any provision for
changing the Device number at all. I guess you could try opening the
drive you finally end up getting, and keep the "cable twist"
idea as a backup.
As example i need to get hold of a new disk drive for use with my
STe, for both HD and DD modes, following my own instructions on this
subject which I did a few years back.
The problem of course if finding one with jumpers to select
between drive 0 and 1.
As far as I remember PC drives have this set to "Drive
1" (or "1") while Ataris need it set to "Drive
0" or "0". Very few drives nowadays have jumpers, but
when I was fiddling around with this stuff I remember that although
drives didn't have jumpers, most of them had small 0 Ohm SMD resistors
soldered on the circuit board, which could be re-soldered to another
position. My question is if this is common on ALL 3.5" disk
drives?
I'm asking because I can't very well ask the dealer to open up the
drive to expose the circuit board before purchasing. The particular
drive I'm possibly buying is a Sony MPF-920-E/131. Anyone know
anything about this one, or 3.5" disk drives in general?
Actually, "Master" and "Slave" are terms which
only apply to IDE hard drives, not floppy drives!
Unfortunately, as you say, ALL 3.5" floppy drives available
today come pre-set to Device 1. Also, as you've noted, most drives no
longer have any convenient way to change the Device setting because no
one ever used it anyway, so manufacturers simply stopped spending the
money on jumpers, headers and circuit board real estate to support the
easy changing of Device numbers.
The ONLY sure way to know ahead of actually purchasing a drive,
assuming you don't find a store that will let you rip one open, would
be to obtain the data sheet for the drive from the manufacturer.
I haven't looked specifically for floppy drive data sheets, but
most hard drive manufacturers have this information easily available
on their web sites. It comes in very handy for the occasional obscure
brand or model whose jumpers are hidden or not marked. If you're
lucky, similar info may be available for floppy drives.
Failing that-
You've no doubt seen the floppy drive cable on an IBM compatible
system with the "twist" cut out section of cable.
The "twist" allows BOTH drives to be physically set to
Device 1. The "twisted" section reverses the drive select
lines so one drive responds as Device 0, even though its jumpers are
set for Device 1. As a "last resort", "bottom of the
barrel", "necessity is the mother of invention"
solution, you COULD rewire the Atari drive cable to simulate this
"twist" and allow a standard Device 1 3.5" drive to
respond as Device 0.
You'd should have a look to the diagram of the IBM floppy cable in
archive to study- once you see how the reversing of the signals is
done it's easier to understand.
There's also a very SLIM possibility that you might be able to
obtain a floppy drive cable which was originally used to connect
QIC-80 style tape drives which had the normal floppy drive female
connectors, but which also had a male connector on it to allow the
tape drive to be inserted into the cable. This could serve as an
"adapter" which would eliminate the need to do ANY rewiring
of the Atari cable. The cable from the Atari would plug into the male
tape drive connector and the new floppy drive would plug into the
"A" drive connector. The floppy drive cable already has the
"twist" needed, and you should be up and running.
The problem would be locating a dinosaur cable.
Technische Daten von:
dennis.vermeire@wanadoo.be
Das SMD-380er ist ein DD-Laufwerk.
Für HD-Betrieb das SMD-340 benutzen und in Atari TT, Mega den
Dipswitch 7 auf "ON" stellen.
Aller Regel nach wird dabei nichts zersört.
Copyright © Robert Schaffner (doit@doitarchive.de) Letzte Aktualisierung am 23. Mai 2004 |
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