Every single time a thread runs, no matter what it is, it drives the CPU at 100% (power-throttling changes the clock speed, not workload saturation). The CPU is a binary device; it’s either processing or it isn’t. When your performance metric tools show you that 100% or 20% or 50% or whatever number, they calculate it from a time measurement. If you see 100%, that means that the CPU was processing during the entire measured span of time. 20% means it was running a process 1/5th of the time and 4/5th of the time it was idle. This means that a single thread doesn’t consume 100% of the CPU, because Windows/Hyper-V will pre-empt it when it wants to run another thread. You can have multiple “100%” CPU threads running on the same system. Even so, a system can only act responsively when it has some idle time, meaning that most threads will simply let their time slice go by. That allows other threads to access cores more quickly. When you have multiple threads always queuing for active CPU time, the overall system becomes less responsive because threads must wait. Using additional cores will address this concern as it spreads the workload out.