Re: [stella] 2600 frying

Subject: Re: [stella] 2600 frying
From: Erik Mooney <erik@xxxxxxxxxx>
Date: Fri, 15 Apr 2005 09:40:52 -0400
On Thu Apr 14 19:44 , 'Fred Quimby' <c9r@xxxxxxxxxxx> sent:

>completely corrupted, just bits and pieces.  But what was abundantly clear 
>was the normal 6502 startup sequence was circumvented.  I know an Apple is 
>not a 2600, but there might be some insight here regardless.

Yes, the normal 6502 startup sequence is definitely circumvented.  Most
2600 games zero out RAM and the TIA upon startup, and if that
happens, the machine is reset to a known state, hence no frying 
effects.  So frying must do something to interfere with getting the
start vector from $FFFC into PC.  I'd guess that there's still noise on the 
bus when the 6502 tries to address $FFFC, causing the PC to get 
initialized from somewhere else instead.

Also, what exactly are you doing with the RAM?  I wouldn't expect a
random sequence of RAM values to accurately simulate frying.  More 
likely, frying just flips a handful of bits in the RAM, and it may be 
more likely for a bit to go from 1 to 0 than the reverse...

- Erik
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