Changes
/* Video */
* The [[CRTC]] should be more or less same as those used in CPCs. The handbook and schematic say the CRTC is a CM 607, but the CRTC in mine [=Kevin's] is an HD6845P.
* The clocks for each mode (0,1 and 2) are derived from the main 16Mhz 16MHz clock, these then drive the shift registers to output pixels to the display.
* Mode 3 is hardwired to 5V, so it doesn't have a clock. The shift registers are stopped and output the last colour they clocked in. Even if this mode was activated in way of connecting up the clock for Mode 0 it is not decoded the same as on the CPC: 8 colours are chosen from the 16 colour palette, instead of 4.
* There may be a bug whereby if the border colour is changed rapidly there could be 1 pixel of another colour output. When loading a game which changes the colour of the border, I have seen moving "snow" on the screen. I have seen this effect, but I need to confirm how it is generated.
