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CRTC

31 bytes added, Friday at 20:54
/* "Rupture For Dummies" bug */
CRTC 1 has a bug that occurs when R5 is updated with a non-zero value when HCC=R0 and VLC≠R9, but only when R5 was previously 0 at the end of the last character line. This disrupts the normal MA reload process, causing the CRTC to load R12/R13 into MA at the beginning of every scanline, regardless of the VCC value.
But if R5 is set back to 0 before HCC reaches The vertical adjustment operates normally after the end of the current character line (when HCC=R0 and VLC=R9)RFD is triggered. If vertical adjustment is not needed, R5 can be reset at any time after the bug won't triggerRFD is activated.
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Phi2x
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