When IVM mode is activated, VLC continues to increment normally. However, RA is not identical to VLC anymore. Instead, VLC is considered shifted left by 1 bit, and bit0 represents the parity of the field (even/odd).
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=== Counter freezes ===
On CRTCs 1/2/3/4, R0 accepts all values without causing any problems for other counters.
On CRTC 0, setting R0 to 0 or 1 will cause some counters to freeze.
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