Re: Bit 0 behavior, take 2

[David Wilson <mcs6502@gmail.com>]

On Jun 14, 3:52 am, Lucas <lscha...@gmail.com> wrote:
> I *assume* that they mean the first bit of the Data Bank register is
> used to select between Bank 0 and Bank 1, which means that one can
> shadow to the SHR screen from any bank in memory.  I thought I had
> heard the MegaDemo used a trick involving this bit, too.

My reading of this is that bit 0 of $C029 (when set) overrides the IIe
compatible alternate memory control bits ($C009 SETALTZP, $C003
RDCARDRAM, $C005 WRCARDRAM etc) and instead uses 24 bit addresses
where A17 is set to access the alternate RAM bank (see table 4-18 on
page 91). I don't think it has anything to do with video modes.