Here is that write up:
Q. When playing O2 games using RGB I notice small flashing dots on screen in different spots based on the game being played.
K.C. Krazy Chase = small red flashing dots in the lower / center part of TV screen.
UFO and K.C. Munchkin = small red flashing dots at the top of the screen
Mage the Final Journey = small red flashing dots at the left of the screen
Any ideas of the cause?
Yes, this is caused by changing the background color mid-screen. With a normal RF connection the dots are too small to notice, but with an RGB connection they are clearly visible. What happens is that when data is loaded into VDC register A3, the write pulse occurs too soon, before the data is available on the data bus. At that moment the databus still contains the address (A3), so that is used as background color briefly before the actual data (color) is written to register A3.
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