[Coco] Coco3 warm start...

Robert Gault robert.gault at worldnet.att.net
Fri Nov 16 08:53:46 EST 2007

William Astle wrote:
> I know I'm probably not seeing something obvious, but there is a point
> that confuses me. I have been tracing the warm start process in the ROM
> and as far as I can see, the warm start process never leaves ROM mode. I
> know it must do so but I just can't seem to find the instruction that
> does it.
> In the cold start path, the ROM to RAM copy process leaves the system in
> RAM mode but the warm start path doesn't do the copy.
> Am I missing something obvious or is something obscure going on?

The code at $C000 is hard to follow and the tendency is to make false 

The reset button will cause the CPU to jump to $8C1B which does force 
the 32k internal ROM mode and jump to $C000. The critical test regards 
this question is the code at $C0DE-$C0E5. $FFA0 is cleared which removes 
the normal $38 block and replaces it with the lowest possible block 
based on available memory. Then $71 is tested for $55. This test will 
fail for Disk Basic but will pass for OS-9 and some other programs that 
"know" about the Coco3.

Since the above test failed, memory is copied from ROM to RAM and the 
system switched back to RAM mode.

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