mooneye-test-suite VS GameBoyEmu

The thing about the Game Boy (or most consoles, really, but especially the Game Boy since it uses a custom CPU) is that we don't know all the details. People have had to reverse engineer it to figure stuff out. /u/gekkio is one of the people doing that work, and his technical reference and test suite are the (ongoing) results of that.

I tested it with the classic dmg-acid2 test rom and another rom called sprite_priority.gb which is part of the Mooneye Test Suite.

I am working on my Game Boy emulator and I'm trying to get the timer to work with mooneyes acceptance tests. Take this one as an example.

The mooneye-gb test suite has very specific tests for the timer (maybe too precise, they require emulating every little detail — but if you want that kind of accuracy, way to go)

I'm making some progress on my my WIP emulator, it has passed Blargg's instructions and instr_timing tests (but is not accurate to sub-instruction cycle timing and so fails the mem_timing tests), dmg_acid2, and mooneye's MBC1 tests. So far, it seems like it can even play Pokemon and Tetris (albeit silently, as I've not yet implemented sound). Yet, when I try running Super Mario Land, it loads up the title screen seemingly fine, but if I try to start the game, it briefly displays the below screen, then returns on its own to the title screen:

My code is on github if you want to look for yourself.

Why is that? Additionally, in the emulator I am trying to develop, which can now pass the cpu instruction tests but not any others of blargg's, when I try to run the same ROM, DIV does not increment for much longer (like 36 opcodes instead of just 5). I have my code available to look at on github, and I am trying to debug but am confused on what's happening now. For the record, I set emulicious to use no boot rom, and my emulator starts immediately at PC=0x100 to skip any boot rom.