Subj : Re: Why does the colour map m
To   : Dennis Katsonis
From : Lawrence Woodman
Date : Fri Dec 18 2020 12:41 pm

On Sat, 12 Dec 2020 13:23:00 +1300, Dennis Katsonis wrote:

> -=> Lawrence Woodman wrote to All <=-
>  LW> Does anyone know why the colour map moves between $9400 and $9600 on
>  LW> the Vic? Is there a reason it couldn't stay at a single location such
>  LW> as $9400?

> I think it had to do with how the VIC chip addressed memory internally.  It was
> only able to "see" a portion of the Vic 20 memory map, and if you moved the
> screen memory, then the color RAM would also have to move so it would map
> correctly.

> http://tinyvga.com/6561

Unfortunately, I don't think it really solves the mystery as while I
understand that the 14-bit address used by the VIC restricts where the
screen map can be, I don't think this alone explains why the colour map
changes between $9400 and $9600 as it uses the same number of bit
positions either way.

Having said that, the link you gave has some excellent information and I
love how it is presented.  Thanks for posting it.

Lorry

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Run Code and Store Data in Display Memory on the Commodore VIC-20
https://techtinkering.com/articles/code-and-data-in-display-memory-on-the-vic-20/

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