But on CRTCs 0/1/2, there is no delay for HSYNC. On CRTCs 3/4, the Amstrad engineers fixed the issue by adding a 1µs delay for the HSYNC signal.
The problem now is that now on CRTCs 3/4, HSYNC occurs 1µs later than on CRTCs 0/1/2. Interrupts being dependent on HSYNC, this is a serious source of incompatibility. It also explains why the CTM monitor has to be calibrated differently on CRTCs 3/4.
==== Discolouration effect ====