Floppy drive pin 2 question?
cctalk at randy482.com
Fri Mar 11 11:57:20 CST 2005
----- Original Message -----
From: "Michael Sokolov" <msokolov at ivan.harhan.org>
To: <cctalk at classiccmp.org>
Sent: Friday, March 11, 2005 2:52 AM
Subject: Re: Floppy drive pin 2 question?
> Randy McLaughlin <cctalk at randy482.com> wrote:
> > Pin 2 on a 34 pin floppy connector is a little used pin. It was used to
> > change the RPM on some 5.25" 1.2mb drives.
> > It changed the RPM from 360 RPM (pin 2 high) to 300 RPM (pin 2 low).
> > was supposed to make it easier to read/write DD disks in a HD drive.
> > Only early AT controllers needed it, later controllers kept this pin
> > and used an odd transfer rate.
> Hmm, my understanding is that pin 2 is LOW when the odd 300 kbit/s
> rate is used, and all HD drives use this pin to switch the write current
> to produce the 300 Oersted field necessary for DD media or the 600 Oersted
> field necessary for HD media.
I am 99.99% sure it changes the RPM, I have some TEAC 1.2's laying around
I'll plug one in and ground pin 2 to check it.
For the TEAC it is enabled via an option jumper, default is to ignore it.
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