[Coco] 512K AND Beyond??? How FAR Beyond???

[Mathieu Bouchard]

The CoCo3 uses a memory mapper chip so that 8 blocks of 8k each because only 64k 
can be visible at once to the 6809. Because the 8 registers for choosing the 
blocks have 8 bits each, you can have up to 256 blocks, which is 2 megs. Beyond 
2 megs, you have to use the mapper differently.

If the OS doesn't test for the possibility of 1 or 2 megs, it's really just a 
detection problem (based on the dumb assumption that no-one would have that 
much), because once it knows how much RAM you have, all the rest works the same 
up to 2 megs.


Le 2017-12-27 à 05:23:00, Joe Schutts via Coco a écrit :

> I have 3 quick questions that I hope the TECHie people (like Ed Zipster and 
> some of the others) can probably answer. The original CoCo 3 came with 128k 
> and then there was the upgrade to 512k. Then someone else (I think it was 
> Disto??) made a 1 Meg upgrade and someone else either built (or designed and 
> did/didn't build) a 2 Meg upgrade. I seem to remember reading an article about 
> it somewhere, but I could be wrong. My question is WHY hasn't someone else 
> like Ed (or even somebody else) built a 1 OR 2 Meg upgrade kit for sale??? To 
> me, this would make an excellent upgrade.
>
> Another related question. If you have a 1 or 2 Meg system, is that memory even 
> accessible from Basic or does accessing it require OS-9 only (or NitroOS-9)??? 
> Last question. Is it possible to access even more memory (higher than 2 Meg) 
> with a CoCo 3 and if so WHY hasn't someone built (or even designed) a board 
> and sell it here??? You listening Ed??? Just kidding... Thanks Everyone... 
> Joe... P.S. I hope everyone had a Merry Christmas and an even happier New 
> Years Eve...

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| Mathieu BOUCHARD --- tél: 514.623.3801, 514.383.3801 --- Montréal, QC