Which output format are you using for the simulation? If it is plt, the entire result-file is stored in memory during simulation.

I'm using mat format

Could you provide a model that exhibits this behaviour?

Unfortunately, due to the proprietary nature of my work I can't share it directly, but I can tell you that I also got several warnings that it got to the maximum number of iterations without being able to calculate the roots (not sure if the two things are related).

What I was hoping is that someone could tell me what "out of memory" means, since the memory usage shown on the Windows task manager stayed around 5GB, and I have 16GB of RAM available on my computer.

Thanks

If you are using Windows, you should know there is a 3GB RAM limit for 32-bit processes. In order to run larger program, you need to use a 64-bit Linux version of OpenModelica.

Any plans for a 64-bit Windows version?

Yes, but if you want something that runs right now instead of (est.) half a year from now, I do recommend running the Linux version.

Windows 64bit is on the way hopefully available next week.
BTW, which version of OpenModelica are you using?

I'm using the latest official release - 1.9.2.