Re: Slot 'extender' dev cable

["David Wilson" <mcs6502@gmail.com>]

On Feb 3, 8:12 pm, pau...@saaf.se (Paul Schlyter) wrote:
> If ProDOS is as good as DOS 3.3... :-) ...then ProDOS too should be
> able to fully access a ProDOS floppy with extra tracks at the end
> (assuming that the ProDOS disk contains correct info about its
> disk geometry).

The ProDOS Disk ][ driver "knows" how many blocks are present on a 35
track floppy and validates the block number passed in before
attempting to read or write the block. The practical upshot is that
you need to patch the kernel (either on disk or in RAM after loading)
as well as the disk formatter program (see Understanding Apple ProDOS
for the addresses to patch [you will need to adjust these addresses
for more recent versions of ProDOS 8]).

As I have a 40 track drive attached to a UDC card I simply updated the
ROM from 35 tracks (280 blocks) to 40 tracks (320 blocks) and I can
run completely standard ProDOS and applications with full 40 track
support.