Cubase Audio Mixdown uses only 30% of CPU?

Making stems, my multiple-channel mixdowns take a long time. Many channels, to 32bit float wavs, using 64bit calculation space. I understand there is a lot of processing involved.

But Cubase is only using 30% of CPU and 26% of memory.

I do not have real-time export enabled.

Any suggestions please how to make mixdowns go faster and/or make Cubase use more resources?