4gb ram 3 gb usable

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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.
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Memory allocationDescriptionHardware ReservedMemory that is reserved for use by the BIOS and some drivers for other peripheralsIn UseMemory that is used by process, drivers, or the operating systemModifiedMemory whose contents must go to disk before it can be used for another purposeStandbyMemory that contains cached data and code that is not actively in useFreeMemory that does not contain any valuable data and that will be used first when processes, drivers, or the operating system need more memory
Note To view how the installed memory is allocated in Windows 7, follow these steps:

1. Click StartCollapse this imageExpand 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.

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.
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Memory allocationDescriptionAvailable Amount of memory (including standby and free memory) that is immediately available for use by processes, drivers, and the operating system Cached Amount of memory (including standby and modified memory) that contains cached data and code for rapid access by processes, drivers, and the operating system Total Amount of physical memory that is available to the operating system, device drivers, and processes Installed Amount of physical memory installed in the computer
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.
Physical memory limits in Windows 7

The following table specifies the limits on physical memory for the different versions of Windows 7.
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VersionLimit in 32-bit WindowsLimit in 64-bit WindowsWindows 7 Ultimate 4 GB 192 GB Windows 7 Enterprise 4 GB 192 GB Windows 7 Professional 4 GB 192 GB Windows 7 Home Premium 4 GB 16 GB Windows 7 Home Basic 4 GB 8 GB Windows 7 Starter 2 GB 2 GB