/vr/ - Retro Games

>>7934887
>Might that also explain using Y scroll values over 239?
No, that's something different and unrelated. The NES is 256x240, so, when you put 240-255 ($F1-$FF) into the scroll register ($2005) as a Y coordinate, the PPU becomes unhappy. It shows "pixels -15 to -1" at the top of the screen, which is erroneous junk from the previous Attribute table as Nametable data.
Here is an example of messing with the Y scroll value and demonstrating what happens when it is invalid: It just shows "garbage" at the top of the screen.