Set How Much Memory is Allocated to Windows

Parallels Desktop is set to allocate a certain amount of your Mac's available RAM memory to Windows and the rest to Mac OS X. If too much memory is allocated to Windows, Mac OS X may slow down, which in turn can cause Windows programs to slow down because they're running on top of Mac OS X. If, on the other hand, too much memory is allocated to Mac OS X, then Mac OS X applications may run well but Windows programs might slow down.

To optimize the performance of both Windows and Mac OS X, set the memory allocated to Windows to be somewhere within the recommended range.

To set how much memory is allocated to Windows:

Shut down Windows .
Choose Actions > Configure > Hardware > CPU & Memory .
Move the memory slider to somewhere within the recommended range, indicated by the graphic under the slider (see above).
If you use Windows programs that require lots of memory, like 3D or video production programs, it's best to set the memory allocation towards the high end of the range (move the slider to the right). If not, it's usually best to set it closer to the middle.

Note: No matter how much memory (RAM) your Mac has, the maximum amount of memory that can be assigned to Windows is 8 GB. However, if you're using Parallels Desktop for Mac Pro Edition, the maximum amount of memory that can be assigned to Windows is 64 GB.

If you change this setting and then you don't like how Windows is performing, then try a different setting.

Note: If you want to prevent Virtual Machine Configuration from unauthorized changes, click the Lock icon at the bottom of the window. The next time someone wants to change the settings in any pane of Virtual Machine Configuration, an administrator's password will be required.