Originally Posted by Mrs Beanbag
of course, AGA machines also have copper, you can change any hardware register approximately every 8 pixels. Writing a 24-bit colour value requires 3/4 register writes though.
Could the OCS copper change a hardware register every pixel? There is a demo (Arte by Sanity) which has the most amazing plasma effect I've ever seen, and it's so fluid it could only be the copper changing a colour every single pixel!
And HAM8 is another query, as well.
HAM6 is simple to understand, the first two bits being:
0 - Colour register
1 - Red
2 - Green
3 - Blue
(OK, maybe not in that order)
and the remaining four bits being used for a value of 0-15 for each one, which makes full use of the OCS 4096 colours, or 12-bit palette.
HAM8 is the first two bits used as described above, but leaving only 6-bit precision (64 levels) of Red, Green, and Blue. So what does AGA do then? Take the colour register with the 24-bit RGB, convert that to the closest 18-bit RGB and then modify the R, G or B in 6 bits?