Re: Color RAM... Can be mapped "out"?

From: groepaz_at_gmx.net
Date: Sun, 30 Aug 2020 14:44:58 +0200
Message-ID: <1810718.b9uPGUboIS_at_rakete>
Am Sonntag, 30. August 2020, 14:23:27 CEST schrieb Marko Mäkelä:
> On Fri, Aug 28, 2020 at 11:52:36PM +0100, smf wrote:
> >You can do that, but registers aren't really what you would consider
> >ram. The 4 bit color ram doesn't particularly count either.
> >
> >Try executing code stored there.
> 
> BTDT, about 26 years ago. You should still be able to find my program
> "dadb" somewhere, and it should work on a decent emulator.  Most of the
> time, the program is executing RTS instructions that are half fetched
> from the color RAM, half from the normal RAM by the previous VIC-II half
> cycle.  The stack is filled with $da, which will cause the RTS to jump
> to $dadb.  It took me a week to write the program, because unlike with
> the predecessor program that was running in open address space ($de00 to
> $dfff), also the least significant address bits matter.  Sometimes, the
> program would have to fetch a non-zero nibble from the color RAM, so
> that it could change the screen color depending on whether the space bar
> was being held down.

here:

https://sourceforge.net/p/vice-emu/code/HEAD/tree/testprogs/C64/openio/

;)


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Received on 2020-08-30 15:02:12

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