Parallels Desktop is a popular virtualization software that allows users to run multiple operating systems simultaneously on their Macs without needing separate hardware or rebooting their machine each time they switch between them! However, some folks have reported experiencing issues with slow performance when using this program. In particular, several users report feeling as though Paralleles desktop 12 runs very slowly compared to previous versions.

One possible cause of these speed problems could be overloading your computer's resources by running too many resource-intensive applications at once within the virtual environment created through parallels itself since windows programs often require more CPU power than their mac counterparts do so try closing any unnecessary background processes before opening up those heavy duty apps again inside vmware player if possible.

Another potential reason for slowness might be related to how you've configured your system settings within OS X itself - perhaps there are certain options enabled under preferences > general that could help optimize performance? For example, enabling 'coalescing' can sometimes improve overall responsiveness when running multiple applications at once because it allows mac os x's window manager (a process responsible for managing windows across all active spaces) to group together overlapping frames more efficiently before redrawing them on screen instead of individually every time something moves outside visible area bounds.

Finally, if none of these suggestions help resolve your issue then consider updating both operating systems involved (macos and parallels themselves), as well as reinstallation might be necessary depending upon nature & severity symptoms described above.

Parallels desktop 12 really slow