Boot Parameters to Manipulate Memory

You can simulate a low-memory environment for testing without changing the amount of physical memory on the computer. Instead, you can limit the memory available to the operating system by using truncatememory or removememory options with the BCDedit /set command.

The /maxmem parameter specifies the maximum amount of memory available to Windows. It is calibrated in megabytes (MB). Set the value to any amount less than the actual physical memory on the computer.

The /maxmem parameter actually determines the largest memory address available to Windows. Due to gaps in the mapping of physical memory, Windows might receive somewhat less memory than the value of /maxmem. For more precision, use /burnmemory.

The truncatememory or removememory options are available in Windows 7 and later. The truncatememory option disregards all memory at or above the specified physical address. The removememory option reduces memory available to Windows by the specified amount (measured in MB). Both options reduce memory, but the removememory option is better at restricting the operating system to use the specified memory while accounting for memory gaps.

Boot Parameters to Test in a Low-memory Environment in Windows

To simulate a low-memory environment, use the BCDedit /set command and the removememory option to modify a boot entry. Set the value of removememory to the amount of physical memory on the system minus the desired memory size for this test.

For example, to limit the memory of a computer with 2 GB of physical memory to a maximum of 512 MB of available memory, set the value of the removememory parameter to 1536 (2 GB (2048 MB) - 512 MB = 1536 MB).

The following example shows a BCDEdit command used to remove 1536 MB of memory from the total available to the system for the specified boot entry.

bcdedit /set {18b123cd-2bf6-11db-bfae-00e018e2b8db} removememory 1536

You can also use the truncatememory option with the bcdedit /set command to achieve the same result. When you use this option, Windows ignores all memory at or above the specified physical address. Specify the address in bytes. For example, the following command sets the physical address limit at 1 GB for the specified boot entry. You can specify the address in decimal (1073741824) or hexadecimal (0x40000000).

bcdedit /set {18b123cd-2bf6-11db-bfae-00e018e2b8db} truncatememory Ox40000000

Because the removememory option makes more efficient use of system memory, its use is recommended instead of truncatememory.

When you are finished testing, you can remove the removememory and truncatememory boot entry options using the BCDEdit /deletevalue command.

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