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No matter its type, the CRTC never buffers any of its counters, except for the video pointer MA. A buffer MA' is needed because MA has to be reloaded at each raster line start.
R12/R13 is loaded only once per frame, in MA and MA', at the first raster line start of the frame. The counter MA is then reloaded with the value of MA' at each raster line start. And at each new character line start, MA' captures the current value of MA.