DISPTMG can be immediately forced to 0 by using R8 (DISPTMG Skew) on CRTCs 0/3/4 or by setting R6=0 on CRTC 1. It is not possible to force DISPTMG on CRTC 2.
=== Interline border ===
On CRTCs 0/2, R1>R0 generates a byte border at the end of the raster line. On CRTCs 1/3/4, it does not.
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