Small red flashing dots

[grips03]

When playing O2 games I notice small flashing dots on screen in different spots based on the game being played.

Example:
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?

[Rafael]

Wow! You've played enough Odyssey these days, cool!

I do not know if that's the case. I do not remember these effects, but you mentioned UFO ...
In Odyssey, destroyed / eaten objects (eg dots on KC munchikin) are actually placed off the screen. Some TVs / consoles show "more screen" than others, you may be seeing part of an object that has been removed from the screen. Again on UFO, sometimes in the interval between the end of a match and the beginning of another, after his ship disappears, if you shoot the shots will appear on the screen. If it is not, they will appear from the top / left position.

[VideopacBelgium]

The dots you seen are due to the RGB quality on the screen.

[grips03]

thanks for the feedback guys.

Marc, that is good to hear as I didn't want to make bad RGB board.  Right now RGB looks really good besides this.  I remember seeing this type of stuff with Atari 2600 games and I think it was related to how game is programmed and off screen stuff.

[Rene_G7400]

When playing O2 games I notice small flashing dots on screen in different spots based on the game being played.

Example:
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.

[grips03]

Thanks Rene

[Rene_G7400]

I've already fixed this issue for a few games a long time ago: Videopac 44, 51 and Frogger. They are included in the C7051 games collection.