OK thanks for trying.
If you can only get 7 FPS then I am not that surprised you couldn't get it to crash. From what I've seen it seems that the crash gets built up to over a little time, resulting from a build up of screen updates/activities that eventually push it over the edge. And it only happens when the game is unpaused, so it's definitely triggered by something that happens when CPU calculation is going on.
Putting that together makes me think that it would need a higher amount of CPU FPS to trigger it - at 5 FPS and 5 GFPS, you're probably not getting enough graphical updates in a short enough amount of time to overload it in the right way. And/or, there's not enough CPU calculating going on while unpaused to trigger the final crash.
Today/tomorrow I will get TWBT compiled locally and then I will be able to debug inside twbt.plug.dll and see exactly what it's doing when it's crashing. Then hopefully I can submit a more precise bug report for mifki.
As an aside, I thought
I had it bad only getting 20-30 FPS on this current game
I can see why you wouldn't want large open areas if you can only get 5-7 from this save. That sucks man. Although you didn't copy my init files - I get 20-30 FPS with Weather and Temperature disabled, and you probably have them turned on. Although I haven't actually measured how much FPS difference turning those off makes.
Also, my FPS varies a lot according to what I'm looking at. If I look at outside (Z0 and Z+1) or some of my busy levels (Z-2, -3, -4), I only get around 20-22 FPS. If I'm looking at levels with fewer buildings/dwarves, then it goes up to 30. I don't quite get why looking at different levels affects the CPU FPS, I would have thought it'd only affect GFPS. But I guess the game does more CPU calcs when you can actually see the dwarves moving about. Maybe when they're out of sight, it uses a quicker/simpler pathing algorithm.
I really feel it's about time Toady made some effort at doing multi-threading so the game can run a lot faster on dual/quad core systems. It's an astonishing, amazing game, which makes it all the more sad that so many users can't enjoy it to the full. It makes me sad that I have to turn off key games features like weather and temperature to get a halfway playable game. And even with those turned off, I still have to limit myself. For example, in this current save if I dig into the caverns at a certain place, FPS drops in half, to about 12-14. So I can't even explore the whole caverns without making the game crawl. I can't enjoy playing when it's consistently less than 20 FPS, it's just too slow and laggy.
It's still an amazing game but it's very sad it has to be crippled in this way. I'd love to get a more modern PC but I can't just drop the it would take to get me a suitable upgrade from this one. My current one was very high end when I bought it, but that was more than 5 years ago. I have managed to keep it relevant by overclocking it heavily (from 2.8 to 4.2ghz) and that's probably why I get so much higher FPS than you. But it can't OC any further and I'm sure it's well behind more modern CPUs on single thread performance, despite the reasonably high clock speed.
It just makes me sad, seeing slow FPS and also seeing the game using only 14% of my total CPU (I have quad core with hyperthreading, which shows as 8 logical CPUs, so 100% of one thread = 12.5% + a few % for the graphics which are the only processing that happens in a second thread.)
Maybe the next version will have some performance improvements. I've seen no mention of them though, so I kind of doubt it. Just lots more features to make the game even slower and/or need to be turned off to make it playable
Anyway thanks for looking into it Leo. Hopefully mifki has enough info to try and fix it, or if it now I will get TWBT compiled and find out where specifically it's crashing.