MT may have improved the performance of that.
Maybe. Some probably. I don't know by how much. They are mere breakings things into to big chunks like sound, physics, graphics, network threads. I don't think they are doing plane by plane threads. It's not that fine grained. And if I have a big arena and some little AI cargo plane is landing delivering supplies off at some base with few around, is it really worth it for it to be calculating complex fluid dynamics for a wake turbulence. If I have a tanker that players are going to regularly line up behind to gas up, then it is worth it there. It's expensive so should be spent where it buys the most improvement in user experience, not waste cpu cycles on unneeded complexity everywhere in places that no one will notice.
Threads, like everything in life is a trade-off not a panacea. More threads mean more cross-thread communication and more complicated thread synchronization overhead.
Multi-threading synchronization is tricky. Really tricky. So there is definitely a curve of diminishing return on complexity. Don't do it right and your multi-threading ends up no faster than single with a lot more risk. Or you end up with dead-lock conditions. Or you just end up with bizarro bugs that are near impossible to track down or reproduce reliably. Which means they are hard as heck to debug and you can't really be sure if you fixed something or if the very specific set of conditions just hasn't aligned to cause it again...yet.
They had an have some bugs from the conversion, but actually I am very impressed they have had as few as they have. Really hard to retro fit threading into something that wasn't designed to work that way from the beginning. But hind sight is always 20\20.
I watched one project I was on pretty much get destroyed by retro fitting in threading and going way to overboard with the granularity. They did the initial conversion in about 6 months and spent the next 3 years try to stramp out all the crazy, random bugs that may not happened for days and suddenly for no apparent reason, suddenly start up. They still didn't have it fully stabilized by the time I told them "Good luck with ALL that" and moved on.
Next they need to do the server.
