Re: Apple IIGS bank latching

[mressl@macgui.com (Marc S Ressl)]

Antoine Vignau wrote:
> (5) returns 02
> (6) returns 03
> (7) returns
> * 1900: 19
> * 2000.2007: 12 34 00 00 00 00 00 00
> * 2080.2087: 56 78 00 00 00 00 00 00
> * 20A0.20A7: 00 00 00 00 00 00 00 00
> * 9D00: 9D
> * 9E00: 9E
> * 9F00: 9F
> * A000: A0
> 
> Antoine
>

Hello Antoine. Now this is most interesting! :-).

Here are the findings:

* The Apple IIe memory switches are always active for bank $E0.
* If the language card and I/O is enabled, Apple IIe memory switches are
active for bank $00.
* If shadowing is enabled for all banks, memory switches are active for all
even banks ($00, $02, etc).
* ROM is always available when the language card is enabled (Sweet16 1, KEGS
0 :-) )
* The New Video "memory linearization" appears to not scramble the contents
of video memory (I'm still having a hard time understanding this, as I
believed it would).

I hope this information is useful to authors of Apple IIGS emulators :-).

With the best wishes,

Mar.c-