Re: Question on ProDOS SmartPort drive remapping

[David Wilson <mcs6502@gmail.com>]

On Dec 5, 7:58 pm, demp...@actrix.gen.nz (David Empson) wrote:
> David Wilson <mcs6...@gmail.com> wrote:
> > ProDOS supports up to 14 volumes but reserves 3/2 for /RAM (v2.0.1
> > forgot to do that and would, if you had enough SmartPort devices, map
> > a drive to it and then overwrite it with /RAM). I have managed to get
> > 15 drives working under ProDOS by using 0/2 (0/1 aka Unit 00 is
> > special and cannot be used).
>
> I thought the unit list in the global page only had room for 14. Perhaps
> it can be stretched by 1 - did it require code patches?

Yes, the global page only allocates 14 bytes ($BF32..BF3F) to store
active device unit numbers but what do we find at $BF40..BF57? A
copyright notice! Overwrting the first few bytes causes no problems at
all. In fact, in later versions of P8, Apple made the byte at $BF40 a
null because much code that changed the device list assumed that there
was a null byte after the last active device and with 14 devices this
was no longer true.