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About memory usage
There are two types of RAM the Macintosh uses: physical memory and virtual
memory. Physical memory is provided by the RAM chips installed in your
Macintosh. Virtual memory is provided when the Macintosh uses the hard disk as a
temporary storage location.
The speed at which the Macintosh is able to access memory depends on what
type of memory it is accessing. Access to physical memory is almost
instantaneous. Access to virtual memory may be reasonably quick or significantly
slower, depending on both the speed of the hard disk and how often the Macintosh
operating system must swap information to and from the hard disk. If virtual memory
requires extensive use of the hard disk, access to virtual memory will be slow.
The more virtual machines you have running simultaneously, the more memory
demands you are making on the Macintosh which results in slower performance.
Installing more RAM in your Macintosh is a cost effective way to eliminate memory
problems and increase virtual machine performance.
In addition:
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Physical RAM is needed by the Macintosh to run Microsoft Virtual PC efficiently. If the virtual machine performance begins to slow down, to increase the speed of
the virtual machine close some of the other Macintosh applications that are
currently running.
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When an application on the virtual machine requests memory, the
Macintosh operating system determines whether physical or virtual memory
will be used. When physical memory is available, the application will use
physical memory that is taken from available physical memory on the Macintosh
computer. When physical memory is not available, and if virtual memory is
enabled on the virtual machine, the application will use virtual memory.
The virtual memory used by the virtual machine is limited by the amount
of available space on the hard disk of the virtual machine and by the
virtual memory setting for the virtual machine. Virtual memory can be
disabled for a virtual machine but it is not recommended.
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The performance of the virtual machine is closely tied to whether
the virtual machine is able to run using only physical memory. Whenever
the virtual machine is forced to used virtual memory, the performance
of the virtual machine may suffer.
See also
About
RAM memory settings
Allocate
memory for a virtual machine