Subj : Why does the colour map m
To   : Lawrence Woodman
From : Dennis Katsonis
Date : Sat Dec 12 2020 01:23 pm

-=> Lawrence Woodman wrote to All <=-

LW> Hello,

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?

LW> I've wondered about this for a while and there is probably an obvious
LW> reason that I'm missing but I would love to know. My interest in this
LW> was renewed recently when I was creating a video (links below) which
LW> shows the colour map being used as a location to store data and now it
LW> seems I really should find out.  I've posted about this on vcfed.org
LW> but there's been no answer yet so am hoping someone here will know.

LW> Run Code and Store Data in Display Memory on the VIC-20
LW>   Video: https://www.youtube.com/watch?v=EkfBijC8MSU
LW>   Article:
LW> https://techtinkering.com/articles/code-and-data-in-display-memory-on-th
LW> e-vic-20/


LW> Best wishes

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

... Dennis Katsonis
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