Re: $DD00

From: Marko Mäkelä (
Date: 1998-10-26 21:29:50

On Mon, 26 Oct 1998, Stephen Judd wrote:

> This last part is very stupid.  Of course it switches VIC banks, as the
> two bitmaps are in two separate banks.  What I meant is that the bitmaps
> are in banks 1 and 2, and I see no way for $DD00 to accidentally point
> to bank 0 or 3 for a single frame.  My thinking is that the garbage might
> be $3FFF or some such.

How wide is the garbage?  Only 8 pixels?  If yes, then it could be that
the $DD00 output lines on the CIA do not change exactly simultaneously
(1->2 could become 1->3->2 or 1->0->2), or they change while the video
chip is reading the data, changing the A14 and A15 during an "address
valid" phase.  I haven't experimented with this; I've always switched
video banks somewhere in the screen border.


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