Some time ago, I noticed that the controller's screen (CWP) of a particular system in a European ACC. was not updating all the visible tracks at once but it was following this pattern:
The screen appeared as if it was split in invisible rectangles. Starting from the upper left corner, only the tracks in a particular rectangle were updated at a time. Then immediately (I think, there might have been some millisecond delay but I couldn't tell for sure) the next rectangle at the right was updated and once all the rectangles on the row were done, the "scanner" moved to the next raw and so on and so forth.
I've seen a similar pattern in another system (in Europe) as well. Is there some technical reason behind this seemingly complex design? eg. could it be the way the surveillance data processing system (SDPS) functions?