Some old thread I tried to maintain to gather info on compatibility modes (before I become dev for OPL):
http://psx-scene.com/forums/f1…odes-openps2loader-63344/
However, none of this mode is intended to improve game speed.
Concerning the rev, it is hard to find or re-compile old ones, as some changes happened in the PS2SDK, so you would have to find and setup an old PS2SDK just for this. Anyway I don't think testing so old versions can bring anything.
For the startup time, I already explained that it is to improve compatibility with most setup/games. That goal is far more important than gaining 2 or 3 seconds when launching a game.
About game format, I'm sure at 100% that the speed doesn't change between ISO and UL format. Use any of these format for your test, the result will always be the same (and btw, 0.7/0.8 supports both format).
Finally, are we agree that general compatibility for games improved ? The opposite would have been a major issue to solve.
I will try to get this game (GodFather) and make some tests.