I noticed some really strange PPU behavior on a Japanese player's Twitch stream recently and am wondering if this is associated with a PPU revision or if it's some kind of hardware failure. Specifically, it looks like the PPU is starting and ending background rendering 1 dot early every scanline, resulting in a duplicated column on the left side of the screen and a missing column on the right side, with sprites being able to hang off the edge on the right.
You can see it in this clip. Whenever Link is walking off the right side of the screen, his sprite is able to extend 1 pixel further than the edge of the playfield, though the background graphics here should extend all the way to the right edge. The background isn't shifted over; rather, the graphics that should be in that column are missing, and the left edge is duplicated. The black regions on the left and right side of the screen are the screen border and correctly output the transparent color on the title screen, so the issue on the left doesn't seem to be some kind of capture problem. I did try to ask the player what hardware he was using and it sounds like it's a normal Famicom, but my Japanese and his English are pretty limited.
Is this a known issue that is perhaps tied to some hardware revision? Does this mean that one can't rely on a sprite 0 hit on that rightmost dot?
You can see it in this clip. Whenever Link is walking off the right side of the screen, his sprite is able to extend 1 pixel further than the edge of the playfield, though the background graphics here should extend all the way to the right edge. The background isn't shifted over; rather, the graphics that should be in that column are missing, and the left edge is duplicated. The black regions on the left and right side of the screen are the screen border and correctly output the transparent color on the title screen, so the issue on the left doesn't seem to be some kind of capture problem. I did try to ask the player what hardware he was using and it sounds like it's a normal Famicom, but my Japanese and his English are pretty limited.
Is this a known issue that is perhaps tied to some hardware revision? Does this mean that one can't rely on a sprite 0 hit on that rightmost dot?