[Please see answers to this related question as well]
The NES Picture Processing Unit has eight memory-mapped registers to the CPU in registers $2000
to $2007
. The are incompletely decoded, so they are mirrored every 8 bytes from register $2008
to $3FFF
.
What does it mean that the memory is "incompletely decoded?" What is the purpose of nametable mirroring in the PPU?