18 May
2023
18 May
'23
4:06 a.m.
On Wed, May 17, 2023 at 8:38 PM Fred Cisin via cctalk
<cctalk(a)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