[Coco] Moving ROM segments to other locations

[Robert Gault]

Arthur Flexser wrote:
> In response to some questions that arose in an off-list discussion
> involving Boisy and others, 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
> 
> 

Good work Art!

I finally got my test code straightened out and can comfirm your 
results. On my system, it does not matter whether the MMU is poked in 
RAM or ROM mode. This pattern extends through all 16 MMU registers.

This is really very strange behavior. It makes you wonder if this is 
involved with the missing trigger for the "256 color mode" in some fashion.