Thanks to our anonymous contributor who managed to patch a model 3 game and run it on real h/w, we were able to obtain some timing values we had been long been missing for correct emulation. The h/w polls something called the ping_pong bit at start-up to sync the GPU with the CPU. Unfortunately we didn't have the correct values and just manually used some per game hacks to get games to run. This mostly worked, but some games were writing more or less frames than they should have been for a given time period. When the ping_pong bit flips at 66% of the frame time, games were writing data for a new frame, which meant writes were often straddling 2 separate frames. We aren't 100% sure if IRQ2 or the ping_pong bit is vblank.