CPU load with multi processing on/off

Hi everyone,

I have been wondering a while now why Cubase on my system (8-core i9 MacBook Pro 16") has a substantial higher CPU load with multi processing support than i.e. Logic or Studio One.

For example: If I open a completely blank project in Cubase 11, the CPU usage of the Cubase process is around 50% (in macOS Activity Monitor - which means 50% of a single core). Overall, this is not much having 8 cores in my machine but nevertheless: The project is completely blank! Logic or Studio One have a CPU usage around 2-3% with an empty project opened.

Now, the strange things happen: 50% CPU load on an empty project only happens if multi processing is turned on in the studio settings (ASIO Guard is off). When I turn multi processing off, the CPU usage of Cubase goes down to 2-3% - the same as Logic and Studio One. Why is that?

The gap even remains if the project has some tracks inside. For example, a project that generates 30% CPU usage with multi processing off leads to nearly 200% CPU usage if multi processing is on. With activated ASIO guard it is even worse.

I have no drop-outs or other problems but on a MacBook the difference in CPU load means a lot in terms of heat and fan noise.

Maybe I am missing something here but hopefully somebody can explain this behavior to me. Why does multi processing or ASIO guard raise the overall CPU usage so much? Logic and Studio One support multi processing, too, but the CPU usage is substantially lower.