Changes
CRTC
,/* HSYNC and VSYNC */
CRTCs 1/2 have a fixed VSYNC width value of 16. VSYNC width can be configured with Register 3 on CRTCs 0/3/4. If 0 is programmed this gives 16 lines of VSYNC.
On CRTCs 0/3/4, even if the number of lines of VSYNC is set to 1 in R3, the Gate Array will perform a full VSYNC of 26 lines(including 4 lines of C-VSYNC). This is also true if the duration of the VSYNC produced by the CRTC is reduced to 2 µseconds.
The bit0 of port B of the PPI immediately replicates the VSYNC signal that is produced by the CRTC.
