SYMPTOMS

On a computer that is running Windows 7, the usable memory (RAM) may be less than the installed memory.

For example, a 32-bit version of Windows 7 may report that there is only 3.5 GB of usable system memory on a computer that has 4 GB of memory installed.

Or, a 64-bit version of Windows 7 may report that there is only 7.1 GB of usable system memory on a computer that has 8 GB of memory installed.

Note The amount of usable memory in the examples are not exact amounts. Usable memory is a calculated amount of the total physical memory minus "hardware reserved" memory.

To view the installed memory and the usable memory in Windows 7, follow these steps:

1. Click Start Collapse this image Expand this image , right-click Computer, and then click Properties.
2. View the Installed memory (RAM) value under System. For example, if it displays 4.00 GB (3.5 GB usable), this means that you have 3.5 GB of usable memory out of 4 GB of installed memory.

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CAUSE

This is expected behavior on computers that are running Windows 7. The reduction in available system memory depends on the configuration of the following:

• The devices that are installed in the computer and the memory that is reserved by those devices
• The ability of the motherboard to handle memory
• The System BIOS version and settings
• The version of Windows 7 that is installed (For example, Windows 7 Starter Edition only supports 2 GB of installed memory.)
• Other system settings

For example, if you have a video card that has 256 MB of on-board memory, that memory must be mapped within the first 4 GB of address space. If 4 GB of system memory is already installed, part of that address space must be reserved by the graphics memory mapping. Graphics memory mapping overwrites a part of the system memory. These conditions reduce the total amount of system memory that is available to the operating system.

For more information about how to determine how memory is used on your computer, see the " Physical Memory Allocation in Windows 7 " topic in the "More Information" section.
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THINGS TO TRY

There are several additional situations that could cause the usable RAM to be less than expected. These issues and possible solutions are listed here:

Check the system configuration settings

This problem may occur because the Maximum memory option is selected incorrectly. To fix this, follow these steps:

1. Click Start Collapse this image Expand this image , type msconfig in the Search programs and files box, and then click msconfig in the Programs list.
2. In the System Configuration window, click Advanced options on the Boot tab.
3. Click to clear the Maximum memory check box, and then click OK.
4. Restart the computer.

Update the system BIOS

The problem may occur because the system BIOS is outdated. If you have an older computer, the system may be unable to access all the installed RAM. In this case, you have to update the system BIOS to the latest version.

To update the BIOS on your computer, visit the Web site of your computer manufacturer to download the BIOS update. Or, contact your computer manufacturer for help.

Check BIOS settings

The problem may occur because some BIOS settings are incorrect.

• Enable the memory remapping feature
  
  Check the BIOS settings to see whether the memory remapping feature is enabled. Memory remapping gives Windows access to more memory. You can enable the memory remapping feature in the BIOS by booting to the system setup. See the User's Guide for your computer for instructions on how to boot to system setup on your computer. The name for the memory remapping feature may be different for different hardware vendors. This can be listed as memory remapping, memory extension, or something similar. Be aware that your computer may not support the memory remapping feature.
• Change the AGP video aperture size in the BIOS settings
  
  Check the BIOS settings to see how much memory that you have allocated to AGP video aperture. This is the memory that the system is sharing with the video card that is used for texture mapping and rendering. This memory would not be used by the system, because it is locked by the video card. You can adjust the AGP video aperture size in the BIOS. Standard settings are "32MB,""64MB,""128MB,"and "Auto." After you change this setting in the BIOS, restart your computer, and then check the usable memory. You can test each setting to see which offers the best results.

Check possible issues with the physical RAM

The problem may occur because there are issues with the physical RAM installed.

• Check whether you have bad memory modules
  
  To check whether you are experiencing this issue, turn off the computer, unplug the computer, and then swap the order of the memory.
• Make sure that the memory arrangement is correct
  
  Refer to the User's Guide of the computer to determine in what order the memory modules should be inserted into the memory slots. The system may require you to use specific slots when you are not using all the available slots. For example, the computer has four slots available. But you may have to use slot 1 and slot 3 if you want to use only two memory modules.
• Check whether memory standoff cards are used
  
  If you use a memory standoff card to hold multiple memory modules on the computer, the system may require specific configurations for this scenario. Therefore, the usable memory may be less than expected.

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MORE INFORMATION

The following sections offer additional information about memory allocation as reported in the Resource Monitor, describe the terminology used, and offer additional information on Memory reporting and memory limitations in Windows 7.
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Physical memory allocation in Windows 7

The following table shows how the Resource Monitor categorizes the memory currently installed on a Windows 7-based computer. Collapse this table Expand this table

Note To view how the installed memory is allocated in Windows 7, follow these steps:

1. Click Start Collapse this image Expand this image , type resource monitor in the Search programs and files box, and then click Resource Monitor in the Programs list.
2. Click the Memory tab, and then view the Physical Memory section at the bottom of the page.

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Memory status in Windows 7

The following table defines the Resource Monitors current reported status of the installed memory on a Windows 7-based computer. Collapse this table Expand this table

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Windows 7 memory reporting

Windows 7 reports how much physical memory is currently installed on your computer. Windows NT-based operating systems before Windows Vista Service P1 report how much memory is available to the operating system. The available memory reported in these earlier versions of Windows does not include hardware reserved memory. This is a reporting change only.

You will see this reporting change in Windows Vista SP1 and later versions of Windows in the following locations:

• The RAM value in Welcome Center
• The Memory value at the bottom of the My Computer windows
• The Memory value in the System Properties windows
• The Total amount of system memory value of the View and Print Details page of the Performance Information and Tools item in Control Panel

Additionally, the System Information tool (Msinfo32.exe) displays the following entries on the System Summary page:

• Installed Physical Memory (RAM)
• Total Physical Memory
• Available Physical Memory

The reporting in the following diagnostic tool has not changed:

• The Performance tab in Task Manager

When the physical RAM that is installed on a computer equals the address space that is supported by the chipset, the total system memory that is available to the operating system is always less than the physical RAM that is installed.

For example, consider a computer that has an Intel 975X chipset that supports 8 GB of address space. If you install 8 GB of RAM, the system memory that is available to the operating system will be reduced by the PCI configuration requirements. In this example, PCI configuration requirements reduce the memory that is available to the operating system by an amount that is between approximately 200 MB and approximately 1 GB. The reduction depends on the configuration.
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Physical memory limits in Windows 7

The following table specifies the limits on physical memory for the different versions of Windows 7. Collapse this table Expand this table

For more information about memory limits for Windows releases, click the following link to view the article on the Microsoft Web site: Memory Limits for Windows Releases (http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx)
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REFERENCES

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
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APPLIES TO

• Windows 7 Home Premium
• Windows 7 Professional
• Windows 7 Ultimate
• Windows 7 Home Basic
• Windows 7 Starter

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Article ID:
978610

Last Review:
May 4, 2010 - Revision: 3.0