How does palette mirroring work?
Palette entry 0 is GOD. It is the most important entry because it determines the background colour, defines transparency for background and sprites, and is mirrored across the palette table. The PPU’s palette table goes from $3F00-$3F1F in its memory. Palette entry 0 is $3F00. But because of mirroring, any changes that you make to $3F00 also directly change $3F10, and vice-versa. Every 4 bytes in the NES palette is also a copy of palette entry 0. Thus, the registers $3F04, $3F08, $3F0C, $3F14, $3F18, etc.. are useless registers. You can write to them, but because they are direct copies of $3F00, there will be no change to the palette. It is because of palette mirroring that only 13 background colours can be shown at once, and not the full 16. • How does PPU mirroring work? Well, there is mirroring across the PPU, in terms of NAME tables. There is only enough physical RAM in the PPU to store 2 different name tables at one time; however, there is still the address space for 4 different n
