Cubase uses only 39% of CPU resources

Audio Performance on the limit. Cubase is choking and unable to work. The system sees 39% of the load. How can it be? How do I fix this?
My system Windows 10.
Cubase 10.5.

Average audio processing load in Cubase does not indicate the same measurement as the CPU usage in Windows.

Your maxed average load in Cubase may have multiple reasons:
Your latency setting
ASIO Guard
Plugin(s)
etc.

If you right click on that graph in task Manager and choose ‘Logical Processors’ you’ll see utilisation of the cores on your CPU. You might see one or two working particularly hard or at 100%. The figure 39% in your screenshot likely points to average utilisation across cores on the CPU.

As Maestro points out too there are other factors to do with how plugins are coded, maybe UAD DSP chips slowing rendering down etc

I turned off ASIO Guard . It got worse. What else can you do?

Looked at “Logical Processors”. None seem to work 100%

Generally speaking, you have to raise the buffer size to be able to utilise more cpu power. The CPU meter in Cubase is showing how much time left when it finished calculation of the last buffer, it is not CPU utilisation meter.

In addition, there is only one FPU component in a physical core, it can’t crunch 2 floating-point calculation at a time no matter how many logical core it shows to OS. Logical core only efficiently works when it does many different operations in a period like calculation, move memory, io operation, etc. But DAW calculation is millions of floating point calc. for dsp against very few integer operation for UI and others, logical core doesn’t help much, that’s the nature of daw.

The maximum buffer size is already set to 1024 samples. The audio card cannot offer more. Is it possible to do something else?

OK then, look for shared effect chain and check routing.
E.g. sometimes it is better to use 2 reverbs than sharing 1.
What is the longest chain in your project? Try to keep the chain as short as possible, try not to share fx, group or side chain the track with others.

On 2nd thought, as the buffer size is already at 1024, there could be something in your system that interferes, you should check with the dpc latency checker or similar.

What is your audio interface?

I have RME Fireface 800. About the chains is an interesting proposal. I have a lot of groups and side chains