Swapping Hi density drives for low density drives

[Michael B. Brutman]

Hi Grumpy :-)

On the Windows 2K machine I used /F:720 to get a 720K format.  On the 
Linux machine I used /dev/fd0D720, which should be equivalent.  It was 
definitely a 720K format, as other parts of the copied DOS 3.3 diskette 
were readable.  Only parts of track zero were consistently bad across 
the multiple diskettes, and they were not flagged as bad on the other 
machines. Even when formatting on the Jr (booted with the original DOS 
diskette and trying to format double density) the format fails.

I wasn't aware of DOS 3.2 and 3.3 falsely reporting media problems when 
straddling a 64K boundary.  I wasn't running with TSRs, but the Jr has 
timing problems of it's own.  I don't think this was the problem though 
- DOS 3.3 was fine.

So it still looks like a double density diskette prepared in a 1.44MB 
drive works fine on modern machines, but isn't quite right when the 
1.44MB drive is running on an old controller.  Like a timing issue. 
Double density diskettes cut on genuine 720K drives work fine.

I'm thinking of getting a special breed of Teac 1.44MB.  It has a 
different model number, and it has jumpers and a modification procedure 
published by Teac to make it a substitute for an original 720K drive. 
That would be an interesting experiment.