How to tune my Virtual Machine for best performance?

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Virtual machine performance is slow either from the start up or while using a certain application. Cause There could be several reasons to the slowness.



The article below will provide you with several steps and hints on how to increase the performance of your Virtual Machine:

  1. First of all, please make sure, that you are using the Download and Install the latest build for your version of Parallels Desktop:

  2. Go to Parallels Desktop menu ► PreferencesAdvanced Make sure detailed log messages are not enabled.

Note: enabling this feature is only necessary while troubleshooting issues related to your Virtual Machine and it may be requested by Parallels Support representative.

  1. Go to the Virtual Machine menu ► ConfigureOptionsOptimization tab ► Set Performance to Faster Virtual Machine; check Enable Adaptive Hypervisor and *Tune Windows for Speed *checkboxes.

In case you are not running on batteries you can also turn on Better Performance option.

3.Go to Virtual Machine menu ► ConfigureGeneral Here you can adjust the number of CPUs and memory assigned for the Virtual Machine. However please note that virtual CPUs and memory are not acting exactly the same as the real hardware CPUs and memory installed on a PC or Mac.

To achieve the best performance we recommend to follow these general tips:

a. In most cases one CPU will provide better performance. Assigning several CPUs for the Virtual Machine may be required in case you run some software that performs a lot of mathematical calculations, such as scientific software or On-line Trades software. If you are not sure if the application you want to run in the Virtual Machine requires more than one CPU just test it with 1 CPU assigned for the Virtual machine. If you see that your Virtual Machine is slow you can try with two or more CPUs.

b. Keep within the Recommended memory range for most cases. More memory assigned for the Virtual machine will not always make it faster.

c. Minimum of Memory assigned to the Virtual machine should be equal to the minimum recommended memory indicated in the System Requirements of the Guest Operating System you run.

d. Maximum of Memory assigned for the Virtual Machine should be calculated from the amount of memory actually used by the operating system when you normally work with it.


You have a Windows 7 64-bit Virtual Machine. You use Microsoft Office Suite, FireFox browser and a couple of other applications on a daily basis. You need to calculate the optimal amount of CPSs and Memory that will provide the best performance for the Virtual Machine.

  1. Go to Virtual machineConfigureGeneral and make sure 1 CPU is assigned.
  2. Check how much Memory is currently assigned for the Virtual Machine. By default is is 1 Gb.
  3. Go to Microsoft web site and check the system requirements for Windows 7.

It says 1 Gb is the minimum required. OK, let's start with it!

4.Start Windows and launch all applications you use on the daily basis: lets start Microsoft Outlook (open several messages there), Microsoft Word (3 documents), Microsoft Excel (a couple of spreadsheets), Firefox (10 tabs), PowerPoint presentation, One Note, Windows Explorer window and Calculator. Now right-clik on Windows taskbar and start Task Manager, switch to Application tab and check how much CPU and memory is used in Windows. You may see something like this:

We can see that all running applications and Windows 7 itself consume about 80% of memory and less than 1% of CPU. It means that 1 Gb of Memory and 1 CPU assigned for the Virtual machine are still enough for all those applications to run in Windows at the same time with good performance. However it may not be enough if you decide to play any flash game or watch Flash video on

Having this information you can either keep the current settings or go back to Virtual MachineConfigureGeneral and add some memory. We would recommend adding not more than 0,2 Gb (256 Mb) or 0,5Gb (512 Mb) at a time. It will ensure both your Virtual machine and your Mac OS X are running at their optimal performance.

For more information about CPU usage in Windows and Mac please refer to the following Knowledge Base article:

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