Re: wildcard in a iie?

[jonnosan <jonnosan@gmail.com>]

I think I've worked out why wildcard is neither running it's own
firmware correctly in my iie, nor letting the Senior PROM see the NMI.

I took a copy of the 2732 EPROM on the card, and it looks like it's
set up to become $F000 - $FFFF. It also is using zero page variables,
e.g.:

F970:  A9 04    LDA #$04
F972:  85 03    STA $03
F974:  A9 A0    LDA #$A0
F976:  91 02 C8 STA ($C802),Y
F979:  D0 FB    BNE $F976
F97B:  E6 03    INC $03
F97D:  A5 03    LDA $03
F97F:  C9 08    CMP #$08
F981:  D0 F1    BNE $F974

So I assume then that when the button is pressed, the wildcard asserts
both NMI and INHIBIT. The INHIBIT signal is necessary to get the
wildcard ROM visible (in place of the motherboard ROMs including the
Senior PROM). However according to the FAQ ( http://home.swbell.net/rubywand/Csa2HDWHACK.html#004
) INHIBIT works differently on the different machines - on the II/II+,
it disables only from $D000 - $FFFF, meaning the zero page accesses in
the code above would work, whereas in the iie, INHIBIT disables RAM as
well, so that code will loop endlessly as $03 will never become equal
to #$08.