Quote:
Originally Posted by Karen O
Mark1960 has a point in post #583.
Were the VDU to assert NENIN part way through a write cycle to screen memory, then that write cycle may be corrupted, resulting in temporary corrupted data in memory. Corrupted data may then show up in the screen display.
When the SC/MP is allowed to resume, the SC/MP will repeat the cycle, complete successfully and restore correct data to memory.
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So, the effect of corrupted display data may be an illusion.
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I do not think it is an illusion as a physical exam of the memory location after a RESET showed the data in the RAM location. Now I have a new pullup on NWDS I have a different effect that does not show up as easily but, it is still a random corruption of memory on write I am sure - the more animation and interactive the program the faster the effect will show up.
I think I will write a character program that just constantly writes the whole visible character set to the top or the bottom with the other side left blank. That should make the corruption visible to the naked eye.
MINEFIELD is the worst (and also the most complex) as using the fire key seems to get it to die quicker than just letting it play itself and burn out tanks.
I think the fact that both Sirius and I see the reverse C in the same place on the 7 segment display is a good sign as we are both getting the same effect in that area of the memory map.
Photo just to make sure it is the same effect Sirius sees.