Amiga Genlock

[JimS]

I'm not sure this thread is oriented to the 7.14MHz CPU clock speed of the 68000 or why it was chosen.

That clock speed is exactly twice the color clock of a composite color video signal. A genlock also derives that clock from the external video that you're trying to super over. The video and amiga need to use the same clock otherwise the overlaid video will shift colors with respect to the amiga... or vice versa. The genlock also derives the horizontal and vertical sync pulses from the external video so the pictures don't roll with respect to each other.

[JimS]

It has no concept of overlay, keying or reverse overlay, thats all internal to the Amiga. The "genlock" then just mixes between the 2 video sources (amiga's output and the external video).

Gotta somewhat disagree here. The only thing internal to the Amiga is the ability to synchronize to external sync provided by the genlock. The actual overlay is done in the genlock.