Using a 1.44MB 3.5inch floppy on an old controller

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Sun Apr 22 14:48:28 2001

From: Michael Brutman <mbbrutman_at_chartermi.net>
>I know that the drive senses the media and adjusts the write
>current accordingly, to get around a bug in older drive
>controllers. But I'm still confused about how the drive
>talks to the controller. The PCjr will still try to format
>a HD disk - it will just fail.


3.5" drives have no intelligence. There are signals that
result from switches that the controller monitors and interprets.
The media in place and media type switches are two such cases.
They can be optical or mechanical but that's not a factor.

>I'm not a hardware engineer, but it would seem reasonable to
>me that the controller and the drive always talk at the 250KHz
>rate, because the controller can't do anything else. For
>double density media this is fine, and the 1.44MB drive looks
>and smells just like a real 720KB drive. However, upon using
>a high density disk, commands to read and write data fail
>because the drive knows it has high density media, but it is
>still talking to the floppy controller at 250KHz (instead of
>500KHz).


The controller or the drive does do some limited things based
on media sensor switch and that is why you must block the
hole to make it work.

Allison


>
>Is this correct? Or does the drive sense that it has
>high density media, adjust it's data transfer rate to 500KHz,
>and then fail because the controller doesn't know what's
>going on?
>
>While we're on the topic, what do people use for archiving
>copy protected disks? I've tried older versions of TeleDisk,
>but it really has a hard time with Sargon III which makes me
>wonder if it is working reliably on my other titles.
>
>
>Thanks,
>Mike
Received on Sun Apr 22 2001 - 14:48:28 BST