Zelda Oracle games: garbage artifacts and lines on screen

[stewmath]

Zelda Oracle games: garbage artifacts and lines on screen

[Stewmath]

I've nearly beaten Oracle of Seasons, and this has been driving me insane, but I never got around to looking very far into it. Now I have. It happens when hblank interrupts are invoked really late - as in, after hblank.

I've made a slight change in the hblank handler. The effect is inverted, but somewhat more mild. Now there is occasionally a white line jutting out below where the status bar is supposed to end, but it doesn't happen very often unless in fast forward mode.

[Stewmath]

Excellent news - I accidentally fixed this completely. Apparently using DMA to copy the tile maps to vram in my "drawScreen" function interfered with hblank interrupts. I was reworking it a bit to be a little more efficient, and the flickering present in a lot of games, including this one, has basically disappeared.

[etking]

The issue is fixed in Zelda but the same problem still exists in Super Mario Land, garbage lines are displayed quite often on the upper area of the screen.

[Stewmath]

The cause is actually completely different. Zelda's issue was with my graphics rendering, whereas Super Mario Land is a problem with gameboy timings - a very low-level issue. Even bgb has garbage on the topmost line. I don't have a real cartridge handy to test with, but if you have one, can you confirm that this doesn't happen (even slightly) on real hardware?

[etking]

I'm 100% sure this does not happen on real hardware, I played through the game quite often back in the day.