Changes
CRTC
,/* CRTC Differences */
=== VTAC overflow ===
During vertical adjustmentmode, if Vertical Total Adjust (R5) is changed with a value less than the current VTAC, then:
* on CRTCs 0/1/2, VTAC overflows and will continue to count up to its maximum value (31) before looping
* on CRTCs 3/4, the current line is considered the last one of the current frame and vertical adjustment ends
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=== VCC (C4) overflow ===
On all CRTCs, if Vertical Total (R4) is updated with a value less than VCC:
* if this update was done when VLC < R4, then VCC overflows and will continue to count up to its maximum value (127) before looping
* if this update was done when VLC >= R4, the decision has already been made to switch to vertical adjustment or vertical border mode and no update to R4 will make the CRTC change its mind for the current frame
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