[Coco] 64K Coco mode and the MC6883

[Allen Huffman]

> On Mar 24, 2023, at 9:34 PM, Sean Conner via Coco <coco at maltedmedia.com> wrote:
> 
>  I was recently doing some retro programming for the Coco-2 (using the
> xroar emulator) that required me to set it up into the 64K RAM mode.  I had
> fun writing what should be the fastest way of doing that [1] but some people
> asked some questions about the code and it got me wondering *why* the code
> works.
> 
>  One question is why we have to toggle the ROM/RAM for each copy?  Why
> don't writes to ROM just pass to the underlying RAM?


I am interested in this topic.

It was only last year that I was watching a video (Robin, 8-Bit Show and Tell) about Commodore 64. He did a thing that did a long PEEK/POKE loop to copy BASIC in to RAM and then another thing to enable RAM mode, then BASIC could be modified.

I had no idea that was possible (I started with a VIC, but moved to the CoCo because the C64 was $600 at the time). It made me curious about what allowed that on the 6502 system but not on our machines.

--
Allen Huffman - PO Box 7634 - Urbandale IA 50323 - 515-999-0227 (vmail/TXT only)
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