If you have access to a Gimix SS-50 6809 or 6800 system, Gimix used the WD1791 in their double density disk controller.  That controller can do single and double density 5 1/2" and 8" disks (250KHz, 500KHz & 1MHz data rates).

On 5/17/2023 2:38 PM, Fred Cisin via cctalk wrote:
As for the target machine having a serial port, one of the machines I
want to get stuff onto is an Osborne 1A. The serial port on that is
horrible.

On Wed, 17 May 2023, Robert Feldman via cctalk wrote:
For CP/M computers such as the Osborne, you can read and write their diskettes on an MS-DOS computer with a program like Media Master. KayPro disks are harder, as there are problems formatting them on an MS-DOS computer.

The earliest Osbornes were single density with ten 256 byte sectors per track.  I was able to write some code on TRS80 model 1 to read those.
Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density.

Then Osborne came out with a "double density upgrade".  The MFM/Double-density Osborne disks are easy to do with PC, if you are familiar with INT13h and INT1Eh.

But, my original stock 5150 PC could never read the original/early Osborne disks.


Single sided Kaypro disks were not hard to do.  Nothing special, other than smaller than ideal inter-sector gaps to squeeze ten 512 byte sectors per track.

But, the double sided Kaypro disks had an incorrect value in the head number field of the sector headers of the second side!  The WD controller used in the Kaypro ignored that field, but the NEC FDC insisted on a match.  I tried some double-sided Kaypros, and found that they would work fine with disks that had the correct value in the head number field.  So, I could format the disks in Kaypro double sided format on the PC, then copy files to those pseudo Kaypro disks on the Kaypro, and bring themback to the PC to read.

--
Grumpy Ol' Fred             ci...@xenosoft.com

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