On Wed, May 17, 2023 at 8:38 PM Fred Cisin via cctalk <cctalk@classiccmp.org> wrote: > 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.
It's odd... The Osborne had a double-density-capable disk controller chip (WD1793) from the start. The double density board is the necessary data separator and write precompensation stuff. I have it in my Osborne, thankfully. I also have the 80 column 'Screenpac' upgrade, which is not relevant here. -tony
