@kojack @eniko I can't remember EXACTLY how it was, but I think the reason of "bitplane vs planar" was to conserve memory/had to do with ( slow ? ) memory access time used on the Amiga. It was an HW limit reason,I know, like the ZX Spectrum has that particular mem patter owing to limitations in the ram access times and limited circuits ( cells ) on the ULA ( yes I have 'The ZX ULA book' ) .