Yay, now I need some Osborne boot media!

[Warner Losh]

>> Later versions of MS-DOS (I don't recall exactly when, but I think it
>> was around 3.3 or earlier, have a DRIVER.SYS installable driver to
>> handle the full 720K)--otherwise, you may be restricted to writing 360K.
> 
> THAT would be version 3.20   of bothe MS-DOS and PC-DOS.
> They also had DRIVPARM as a CONFIG.SYS "command", that would reconfigure
> without adding another drive nor driver in [precious] RAM.  But, that was
> not documented in the PC-DOS manuals, and for reasons as yet unexplained,
> would not work with the real IBM BIOS ROMs, although it did work [with
> either PC-DOS OR MS-DOS] with Award, Phoenix, and several generic BIOS
> ROMs.
> 
> Also, SOME non-generic OEM versions of 2.11 that were put out with laptops
> supported 720K drives.

All this talk reminds me if the IMPDRIVE driver I wrote for my Rainbow
back in the day so I could connect the 720k floppy drives to it and have
them work. IIRC, it was little more than a thin wrapper to properly setup
the parameters for the Rainbow’s default driver to access them correctly.
Fun times.

Warner