This may be something interesting for those who compile Irrlicht frequently, or otherwise have large projects to handle.
I've been experimenting with using unity builds to speed up compilation times, and here's what I get with my (old) machine, and the unmodified Irrlicht 1.4.2 source, full rebuild:
The original compile time is already quite fast, but halving it is definitely sweet, and I'm sure more improvements are possible if the source files are modified.Release build: 2 mins to 1:04 mins
Debug build: 1:23 mins to 0:28 mins
For those who are interested, more details and project file download can be found on my webpage
