On CRTCs 1/2, this mode increments VCC, causing it to exceed R4, and this increment can happen multiple times depending on the values of R5 and R9.
Also, only CRTCs 1/2 have a dedicated C5 counter. On CRTCs 0/3/4, during Vertical Adjustment, C9 has to fullfil the VTAC role which means that it cannot plays its VLC role. This impacts address generation.
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