[Coco] Memory paging on the coco3

[Robert Gault]

Stock Coco3 has 128K but most of this is reserved for the high res text 
and graphics screens. Normal Basic still has 64K to play with.

Memory on a 128K Coco3 maps:
$60000-$68000 high res graphics, MMU block, $30-$33 or 48 - 51 decimal
$68000-$6C000 stack and graphic buffers,    $34-$35    52 - 53
$6C000-$6E000 high res text,                $36        54
$6E000-$70000 free,                         $37        55
$70000-$7FFFF Basic, Disk Basic, Super Extended Basic $38-$3F, 56-63 dec

Note that memory addresses do not start at $00000 on a 128K machine. 
This locks the memory common to both 128K and 512K (or 2Meg) Coco3s to 
the same addresses. The 512K and higher add from $00000-$5FFFF and 
$80000 - up.

The relationship between MMU blocks and memory is MMU# times $2000 
equals starting address. ex. $38*$2000=$70000

Frank Pittel wrote:
> In an attempt to find some documentation on how the memory
> paging on my coco3 works I did a lot of googling and finally
> posted the question on one of the forums on the coco3 site.
> 
> I did get pointed to a site that does a rather complete job
> of describing the gime chip and how the paging works. It all
> looked good until I got to the bottom of the memory mapping
> chart and read how the memory is map as 8K pages. According
> to the page on a coco3 with 512K of ram the pages used are
> numbered from 0-63 which multiplies out to 512K. Then there's
> mention that on a "stock" 128K coco3 pages 56-63 are used.
> Another check with the calculator and I find that works out
> to 64K of ram. I always thought that my Coco3 had 128K of ram.
> 
> Exactly how much ram does my coco3 have and what are the memory
> pages used to access it? Of course now I'm thinking that the
> best solution would be to upgrade the memory to 512K and not
> worry about it anymore.
> 
> 
> Frank
>