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The most interesting point for the TAS on this game is that in order to get the best and fastest stats so far in any% is faster than any TAS could ever do it because it requires RNG set up from the previous attempt and the TAS timing would include that entire setup.
I've made good progress on screen timing and now can get pixel accurate frames even for timing sensitive games like Speedway above.
I also figured out the (probably) correct emulation for Blockout, which is much simpler and more realistic then what I was doing before. The key is that the VBL flag bit is reset upon read, not upon end of VBL. It's more of a 'VBL needs servicing' flag then a 'VBL in progress' flag. I probably should have guessed this earlier since the sound bit works the same way.
There are still a few finer details that need to be sorted out, but I think all the major timing challenges are dealt with now.
Please revive the C++ version of GBHawk. So I can use it.
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I did a lot of rework on the ppu and now things are working much better.
Blockout behaves like console now, as does Cosmic Conflict, which is now closer to console then O2EM.
The good thing about Cosmic Conflict and Blockout is that they both do fairly careful timing things but in different ways, so if they are both correct at the same time it's a pretty solid indication that the emulation is close to correct.
A big open end remains in that Blockout turns on HBL interrupts but expects them to not happen. I don't know what's up here, I would need to find a game that actually uses HBL interrupts constructively to do things correctly but so far I can't find one.
Anyway as always more testing is appreciated. I think I'm getting close on NTSC, PAL still needs some work though.