27 May
2021
27 May
'21
1:47 p.m.
On 5/27/21 12:21 PM, Fred Cisin via cctalk wrote:
In 1981, when the Osborne 1 came out, I got some
sample disks from it.
So, other than TRS80s, which I had, those were also the first samples
that I worked with.? I manually, a sector at a time, copied some files
from those Osborne 1 disks using Superzap on TRS80.? THAT was the
preliminary success that convinced me that it could be done, and gave
the the impetus and confidence to write XenoCopy, in the next few years,
after the 5150 came out.? (5150 came out August 11, 1981, but it took me
5 months to get one)?? BUT, the 5150 couldn't do FM Single Density, so
the PC-DOS version of XenoCopy didn't get an Osborne format until the
MFM Double Density upgrade for the Osborne 1 came out.
I'd been cutting floppy controller code since about 1975; the weirdness
of the IBM PC design really made for some head-scratching.
Sometime in the 5150/5160 days, I published instructions on how to
modify a PC floppy controller that used the 765 with a WD926 data
separator. It was quite simple--for some unknown reason, both of the
clock rate select lines were hard-wired. Getting FM support was mostly
a matter of lifting one of those lines and running a jumper to the
MFM/FM output on the 765.
But then IBM and clones did the same sort of thing with the parallel
port adapter. Changing one to bidirectional (and curiously
PS/2-compatible) was mostly a matter of lifting the output enable line
on an IC and tying it an unused bit in the control port.
Sometimes I wonder if IBM did this sort of stuff intentionally.
--Chuck