How to read Osborne 1 Floppies?

Fred Cisin cisin at
Mon May 24 13:26:41 CDT 2021

There were two Osborne floppy formats.  Both CP/M.

IIRC, the original format was "Single Density" (FM), 10 sectors per track, 
with 256 bytes per sector (similar to the TRS80-Model-1.  That will 
require FM/SD capability.  Most NEC FDCs did not support that.  Dave 
Dunfield has a test program that will tell you whether your FDC can handle 

Then, they switched to "Double Density" (MFM) IIRC: 5 sectors per track, 
with 1024 bytes per sector.  Any PC FDC with access to INT13h and INT1Eh 
will work with appropriate software.  (NOT external USB drives)

WITH appropriate software, a flux transition device, such as your 
Catweasel, could do it.

On Mon, 24 May 2021, Zane Healy via cctalk wrote:

> A photographer I know contacted me last night asking about reading Osborne 1 floppies.  What does it take to read these?
> The only Catweasel board I have is the old Zorro 2 board for the Amiga.  I do have 5.25” floppy drives.  Neither of us have an Osborne anymore (I think mine went to Jim Willing).
> Zane

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