When I start Massive 101 on my Machine (AMD Ryzen 9 9950X 16-Core Processor (4.30 GHz). Windows 11), it tells me in a window, that it only uses 8 threads instead of the possible 32.
Massive doesn't try to use all available threads, but you can set the number of threads using the -threads command line option. If you don't want to start Massive 101 from the command line then you could start it from a batch script.
