==== R3 fine horizontal hard scroll ====
If R3 is set to 5 instead of 6 or more, then the frame is shifted to the right on the display CTM monitor with an offset of half a CRTC character on a CTM monitor. This is due to the effect of shortening the C-HSYNC produced by the Gate Array. As this effect relies on invalid video signals, it is badly supported on modern displays.
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