Re: Airheart and Prince of Persia Not Detecting Memory on My IIe

[dempson@actrix.gen.nz (David Empson)]

Tempest <tempest@atariprotos.com> wrote:

> On Aug 24, 9:26 am, Tempest <temp...@atariprotos.com> wrote:
> > On Aug 24, 4:27 am, mdj <mdj....@gmail.com> wrote:
> >
> > > On Aug 23, 10:37 am, Tempest <temp...@atariprotos.com> wrote:
> >
> > > > Anyone have any idea as to what the problem could be?  I've reseated
> > > > every chip and card, so I'm starting to wonder if something is blown
> > > > that I can't see.  But the system passes all diagnostic tests.  This
> > > > is really weird.
> >
> > > Do you have anything in slot 3? </longshot>
> >
> > I don't believe so, but I'll check tonight.
> 
> Eureka!  I had my mouse card in slot 3 instead of slot 5 where it
> normally is.  I must have put it back wrong when I was swapping things
> out last year.  I have no idea why this would cause the Apple to not
> see the 128K of memory, but apparently it does.  Go figure.

Ah, that gives enough of a clue to work out what was probably going on.

A mouse card in slot 3 would block access to the 80-column firmware,
including the AUXMOVE and XFER entry points for accessing the main 48K
region of auxiliary memory. This would prevent some programs from being
able to use auxiliary memory.

ProDOS might still be able to use auxiliary memory as a RAM disk,
because the /RAM driver lives in the language card area so it can
control the main 48K soft switches directly. It has to implement its own
code for using auxiliary zero page and stack anyway, and that part runs
from auxiliary memory (somewhere in $0200-$03FF if  I remember right).

AppleWorks has its own auxiliary memory driver, which could function
without using AUXMOVE and XFER if it was loaded into the auxiliary
language card.

-- 
David Empson
dempson@actrix.gen.nz