5.25 floppies that read but don't write

Chuck Guzis cclist at sydex.com
Sat Aug 22 00:08:31 CDT 2015

On 08/21/2015 09:50 PM, Marc Verdiell wrote:
> Chuck, I looked at the pin 2 signal and resulting drive behavior. It
> doesn't properly auto-switch between densities as it should. It does
> switch it for reading, but not for writing. Below is the full story.

On 5.25" HD drives, pin 2 is generally a drive *input*.  That is, the 
host telegraphs what's needed, not the drive.

This is different from the 3.5" world, where HD and 2D floppies have a 
mechanical means (density aperture in the jacked) to indicate what's 
needed.  Some drives/systems can work together so that the drive 
determines which media type is inserted and notifies the host.

But not in the 5.25" word.


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