Renoise indeed does show a different CPU than task manager. It shows the “relevant” CPU usage, the CPU usage which currently is used in order to calculate audio in real-time.
In other words: how much CPU power in your current setup currently is used in order to be able play back the song. Everything else would be misleading because it’s simply not relevant for real-time audio processing.
Lets say you have 8 CPU cores and are playing back a single VST instrument with all 8 cores enabled.
In …
I had paraphrased from memory, perhaps I should have linked to this. Although I remember reading a different Taktik post as well but I can’t find it now, sorry.