blastar (./27) :
Razoola, thanks for suggestion.
updating 250 palettes takes more time than expected - i have to disable screen while updating... works very well and it's pal-save!
(re)moving BIOSF_SYSTEM_IO saves some rasterlines but not enough.
with this code it's possible to update all palettes within one frame... this small multicolor-effect runs now with 60fps!

Nice to hear that!

Could you change the circle colors of the multicolor effect to be modulated by a sine of different length (e.g. sin(radius*2) for blue, etc.)? This should give nice smooth concentric circles for some contrasts and help investigating the pixel modes regarding their effect on the perceived resolution.