Quote:
Originally Posted by SiriusHardware
Can't be the current character as that is changing at the rate of a zillion per second with the reduced timing delay, but the character below the 'M' in your name only changes maybe from one minute to the next. I think that's an unintentional change but I will have another look at it.
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Indeed just checked there is only one store instruction - I have done the same test and nothing else is changing for me onscreen even with no DLY so it seems that is your marginal effect.
That effect gets worse when you use a 10K resistor (and appears to be the same area of the screen as me so I was pleased you get almost or the same effect) - that even shows the double write of both RAM's accepting the data as CS must be changing as well so they both act on the corrupted address (in the range of the real one it seems) to action the low NWDS and get mostly the correct data from the data bus - as of course the VDU does not affect that as it is expecting to only read the bus once the memory chips drive it.
This is consistent with the correct data being written to the wrong location. I.e. your pattern of Valid characters is the pulse pattern where the write goes wrong and occurs on the same characters as of course the timing for their appearance is very precise.
MINEFIELD stores its variable near the start of its code so is highly likely to corrupt itself - for me that happened a lot after level 2 which is where the code is self modified to increase the speed.