In Windows, a program cannot allocate or dedicate cores for execution; it is the responsibility of the operating system to allocate processes and threads across cores.  Avanti requests that each simulated Alpha CPU thread be run on a separate physical core by setting the affinity of the virtual CPU thread to the desired core number and requesting that the simulated Alpha CPU thread run at highest priority.  This should give the virtual Alpha CPU thread exclusive access to that core, provided Windows honors the request.

There are various other threads created by Avanti which take care of asynchronous IO to disks and Ethernet controllers, but these are requested at normal priority, and can be freely scheduled across available cores.

Note that Windows is free to ignore Avanti affinity and priority requests.  Also note that if there are enough physical cores to run the desired workloads, system performance can be increased by disabling hyper-threads, which will give a speed boost to the physical cores since they no longer have to co-schedule the hyper-threaded virtual cores.