Yeah, i think so too. In Vice City the most surprising thing to me was that they actually modelled tire temperature. it's probably a bit crude but i found it interesting. As for the physics code, there's a big ProcessControl function all sorts of physical entities that does everything that has to happen to that entity each frame. some of it is physics, some not. My theory as to why varying timestep produces different results is that the physics calculations form some sort of differential equations whose solution depends on the timestep. That may be wrong but it makes sense to me at least. My approach to fixing it would be to log all sorts of forces applied to the physical objects each frame and log them so they can be compared. this is quite a bit of stuff to implement though so nobody has done it yet. if you or somebody is interested in that, we'd appreciate that a lot.

The physics engine of Vice City is definitely tied to the frame rate. If you switch off vsync, you can only drive in reverse veeery slowly.

That one i was actually able to fix :)

Ha, back in that same era I was working at a small game company that was in discussions with Papyrus about doing some work on the Indy Car Racing game - probably a Playstation port. It never happened - I think it was determined that it wouldn't sell enough to cover the development costs. I don't remember much else except we played the PC game ("research") and it was super difficult - you needed a lot of skill not to crash at every curve. I also seem to recall that the polygon models for the cars were based on manually edited text files. Good times.