[Coco] [Color Computer] Hardware specifics regarding GIME , RAM and ROM

[Mike Pepe]

> Actually, that's incorrect, though the ROM segments respond in a
> different way to changing the MMU values than RAM segments do.  We had
> a thread about this a while back.  Particular ROM segments can only be
> moved to certain addresses, and what address you pick determines which
> ROM segment moves there.  You can even move segments from the internal
> patcher ROM, which is normally inaccessible, to locations where you
> can see them.  It works in a very weird way.
> 
> Here's part of a message I posted to the list back in April of '04
> that gives details:
> 
> Here's what happens as a result of moving ROM segments around,
> according to some old notes I dug up, where all MMU pokes
> are done in ROM mode:
> 
> MMU location    Value          Segment moved
> Destination
> 
> $FFA0        $3C or $3D      I0  ($8000 Extend. Bas.)           $0000
>                     $3E or $3F      E0  ($C000 External ROM)
> 
> $FFA1         $3C or $3D      I1  ($A000 Color Bas.)
$2000
>                      $3E or $3F      E1  ($E000 External ROM)
> 
> $FFA2        $3C or $3D      I2  ($C000 Int. Basic patcher)   $4000
>                     $3E or $3F      E0  ($C000 External ROM)
> 
> $FFA3        $3C or $3D      I3  ($E000 Int. Basic patcher)    $6000
>                     $3E or $3F      E1  ($E000 External ROM)
> 
> 
> I haven't actually verified the $FFA0 results, but inferred them from
> the
> pattern of the others.:
> 
> 
> 
> Art
> 

Art, that seems contrary to what the GIME design specs and the service
manual say, but it is certainly worth investigating.

I'm not sure how that works exactly since the MMU registers are
apparently not initialized by a reset from what I've seen. 

-Mike