=== MA buffering ===
No matter its type, the CRTC never buffers any of its counters, except for the video pointer MA. The buffer MA' is needed because MA has to be reloaded at the beginning of every raster line.
At the end of the display of the last raster line of each character line (ie. when HCC=R1 and VLC=R9), MA' captures the current value of MA.