Bug report: Notice that sprites have up and left wraparound issues, especially noticeable in Super Mario World, you can easily test it in water levels by going off-screen with Mario.

Anyway, time for me to check how the Nintendo Super System BIOS works, it's a z80 plus external video output (M50458 - Mitsubishi M50458-001SP On-Screen Display (OSD) Chip (NDIP32), I haven't found any manual so far, Stiletto? wink ). I've got to the point that it loads the Instruction ROM, and then it waits for a vblank irq ... by doing this:

13EC: 3E 10 ld a,$10
13EE: ED 47 ld i,a
13F0: ED 57 ld a,i
13F2: FE 10 cp $10
13F4: 28 FA jr z,$13F0
13F6: C9 ret

RISC-style IRQs anyone?