Writes to OAMADDR should corrupt OAM. #5
Description
On original hardware, writes to OAMADDR cause the values at the 8-byte block of OAM previously pointed to to be written to a non-random location. Additionally, a value in OAMADDR greater than 7 will cause that 8-byte chunk to be written to the start of OAM. This corruption must be emulated to ensure full compatibility.
More details on this corruption behaviour can be found here.