[Coco] GIME Question

[Arthur Flexser]

Were you in ROM mode when you compared the contents of $BFF0 and $FFF0?

To access ROM mode there, you may need not only to poke $FFDE, but also diddle
the "constant RAM at $FE00" bit in one of the GIME registers.  (The latter
requires disabling the IRQ first -- POKE &HFF03,&H34 -- to avoid a crash.)
 
Art


On Sun, 10 Jun 2007, Darren A. wrote:

> The SAM in the CoCo 1/2 maps addresses $FFF0 - $FFFF (interrupt/reset 
> vectors) to $BFF0 - $BFFF (End of Color Basic ROM). Does the GIME not mimic 
> this behavior? On a CoCo 3, PEEKing at &HFFF0 returns a different value than 
> a PEEK at &HBFF0.
> 
> I wanted to burn an EPROM with a new address for the 6309 illegal 
> instruction vector, but my initial tests under MESS didn't work when I only 
> changed the address at $BFF0.
> 
> Does anyone know of a simpler way to change the COCO 3 ROM without having to 
> completely desolder the original? I'm kind of afraid to undertake such a 
> project. The CoCo 1's socketed boards are so much easier to tinker with.
> 
> Darren
> 
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