I’ve just released Alpha17b, a performance hotfix for Alpha17. Steam users will get it automatically. This is build 0.17.1557.
When we made the targeting AI smarter in Alpha 17, we also made it harder on the CPU. Players in late game were seeing drastically reduced performance. Alpha17b optimizes this and several other things. There are no changes to gameplay - just optimization of what's there already.
This update will work with your existing saved games, XML-only mods and (hopefully) most or all code mods.
If for any reason you want to continue on the older version, you can set your Steam beta branch to 'alpha17a'.
Sorry for any disruption! We’re also hard at work on Alpha 18.