On 5/5/22 16:50, Mike Katz via cctalk wrote:
If you use a 80 track (96 TPI) 5 1/4" drive to read 40 track (48 PTI)
floppies that will work but if you write onto them they will not be
readable in a 40 track drive any more. The reason for this is that the
had is half the width and when the 80 track drives writes to a 40 track
written disk it only overwrites half of the track. And when the 40
track drive goes to read the data it sees nothing but noise because the
two halves of the track are different.
Well known and documented back when we first started using 80 track
drives.
If you want to write floppies on an 80 track drive and read them on a 40
track drive. Magnetically erase the disks with a demagnetizer and then
format the disk in the 80 track drive but double stepping the format.
I always erase floppies with my tape degauser before formatting. Even
new disks usually have some pattern written on them.
Double stepping means writing track zero on physical track zero and then
writing track 1 on physical track 2 and track 2 on physical track 4, etc.
This avoids the problem of tracks with different data on each half of
the track. The 40 track drive will only see the half track data.
Not all operating systems nor drivers can handle this.
Gimix Flex for the 6809 could handle this as a special configuration.
I'm sure you could get the greaseweasel to support this also.
I just got a GreaseWeazle. Not impressed so far.
I hope this helps.
All information helps.
bill
