How to Calculate Maximum Available Physical Memory


The amount of physical memory that can be safely allocated to a given product varies from system to system. While all products can manage the maximum limit that the particular Windows operating system platform permits, memory should be reserved for the operating system itself, and for the various processes (services and applications) that will be running. Additionally, when active, each product allocates a small amount of physical memory for overhead.

For systems with relatively small amounts of physical memory e.g. 2 GB then only 60 to 70 percent of the physical memory may be available. On larger systems, above 4 GB, 80 to 90 percent or more of physical memory may be available for the product.


Each version of Windows Servers (2003, 2008 & 2012 Servers) limits the amount of physical memory recognized by the operation system. For example, when Windows 2008 R2 Standard is installed on a machine with 48 GB of RAM. This OS will recognize a maximum of 32 GB. The remainder cannot be accessed by the OS. However, SuperSpeed products can acccess the additional RAM via our patent pending "Unmanaged Memory (UM)" functionality. So in this case the extra 16 GB can be accessed and used by RamDisk Plus or SuperCache Express software!

The maximum amount of available physical memory at any moment cannot be predetermined precisely since it changes even as a system is active. Attempting to allocate the absolute maximum amount may ‘starve’ the system of memory resources, actually reducing its performance, and, in extreme conditions, could lead to a system crash.

Installed RAM

Percent Available

Examples of installed RAM on Systems Approximate RAM available to SuperSpeed products
512MB to 2 GB 60 - 70% 512 MB 300 MB
1 GB 640 MB
2 GB 1.5 GB
4 GB 80 - 90% 4 GB 3.2 GB
>128 GB to 4 TB 95% 128 GB 121 GB

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Last updated: 6 June 2014

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