Certain applications in the virtual machines might perform better with more memory available. Having more memory available to the guest operating system can facilitate caching, which can improve performance of the virtual machine. You can change the amount of virtual memory available to a virtual machine.
For the best balance of performance between Windows and Mac applications, do not give Windows too much memory, because it might cause your Mac to become slower. For Windows XP, 512MB of memory is ideal for Internet and office productivity applications.
For Windows Vista, Windows 7, Windows 8 and Windows 10, 1GB of memory is ideal for Internet and office productivity applications. 1GB of memory is appropriate for both the 32-bit and 64-bit versions of Windows 7, Windows 8 and Windows 10. If your Mac has at least 6GB of memory, Fusion uses 2GB of memory as the default for 64-bit versions of Windows 7, Windows 8 or Windows 10 guests. These settings are the default memory settings for Windows virtual machines that Fusion Easy Install creates.
Prerequisites
Shut down or power off the virtual machine. You cannot change the setting while the virtual machine is powered on or suspended.