Windows - Showing less gb of ram

Wikitechy | 1208 Views | windows | 20 Jun 2016


Windows Showing less GB of RAM Windows Only ShowsAbout 3.5 GB space of a RAM WithMore Than 4 GB 

  • In a Machine with 4GB of physical RAM, Windows is only able to report a portion of the physical 4GB of RAM (ranges from ~2.75GB to 3.5GB depending on the devices installed, motherboard's chipset & BIOS (Basic Input/output System)).
  • This behavior is due to "memory mapped IO reservations".
  • Those reservations overlay the physical address space and mask out those physical addresses so that they cannot be used for working memory. 
  • This is independent of the OS running on the machine.
  • Significant chunks of address space below 4GB (the highest address accessible via 32-bit)gets reserved for use by the following system hardware:
  1. BIOS – including ACPI (Advanced Configuration and Power Interface) and legacy support a video.
  2. PCI (Peripheral Component Interconnect) bus including bridges etc.
  3. PCI Express support for about 256MB to 768MB depending on graphics card installed in memory.
  • Typical system’s memory space is about~256MB and 1GB. 
  • The Intel chipset specsaddress range “1.5GB”is reserved and not acessible to Windows.

Solution :

  • When the complete 4GBspace is required, the only option is to upgrade to a 64bit operating system:
  1. Windox XP 64
  2. Windows Vista 64
  3. LinuxMax OS/X (ok, you may need a new PC for that as well)
  • WindowsXP and Windows 7 are 32bit , and hence there is a limit on memory up to 3.5GB max. 

Applies to :

  • Windows 1
  • Windows 8.1
  • Windows 8
  • Windows 7
  • Windows Vista

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