HAM6 is 6 bitplanes deep and HAM8 is 8 bitplanes deep. The upper two bits select the action:
0 -> the lower bits point to the palette
1 -> the lower bits set the red portion
2 -> the lower bits set the green portion
3 -> the lower bits set the blue portion.
As you can see, with HAM8 only 6 bits are available to modify colors, so you don't get real truecolor but only 262144 different colors (plus 64 from the palette). With HAM6 all 4096 colors can be reached.
What do you want to know more ?
Bye,
Thomas
