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

From: Marko Mäkelä <msmakela_at_gmail.com>
Date: Sun, 30 Aug 2020 15:23:27 +0300
Message-ID: <20200830122327.GA21483_at_jyty>
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.

	Marko
Received on 2020-08-30 15:00:03

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