Bit planes are pretty easy to implement in hardware. One of the nice things is that the bit calculation is the same for each plane so you feed that value, bit o

Bit planes are pretty easy to implement in hardware. One of the nice things is that the bit calculation is the same for each plane so you feed that value, bit offset, and plane start address into a barrel shifter and out pops the bit you want. those you gang together into a register and poof you can read them all at once. The ARM Cortex-M bit mapping memory region does this computation. It also means you can build things like pixel copy of arbitrary width pixels with a single bit copy engine running 'n' times. With memory and transistors getting cheap though, all of that became unnecessary it seems.