Changes
CRTC
,/* VSYNC */
On CRTCs 0/1/2, the sole condition to trigger a VSYNC is that VCC=R7. While on CRTCs 3/4, it is necessary to have VCC=R7 and HCC=0 and VLC=0 to trigger a VSYNC.
=== Blocked VSYNC ===
On CRTC 0, if R7 is modified with the value of VLC when HCC<2, we are in blocked VSYNC. Then, the VSYNC can no longer occur on VLC=R7 until an unblocking condition is produced. Source: §16.4 "Conditions to consider" of the CRTC Compendium
=== Ghost VSYNC ===
