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If you have 4GB RAM in 64-bit Windows 7, how much is actually available?

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You have all 4 GB. The memory restriction you have in mind is only applicable to 32-bit operating systems.

Windows 7 64-bit has limitations on the amount of memory based on the editions:

  • Starter: 8GB
  • Home Basic: 8GB
  • Home Premium: 16GB
  • Professional: 192GB
  • Enterprise: 192GB
  • Ultimate: 192GB

See this comprehensive list for all memory limits of the various versions of Windows.

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Provided the chipset and BIOS remap the RAM shadowed by I/O. – Ignacio Vazquez-Abrams Mar 10 '11 at 19:22
True. How can the OP check if this is the case? Would a 32-bit limitation mean that only 3.2 GB is displayed during POST? – Paul Lammertsma Mar 10 '11 at 19:25
All 4GB will be displayed at POST; the actual amount available can only be verified in the operating system since any remapping will have happened by that point. – Ignacio Vazquez-Abrams Mar 10 '11 at 19:26
My motherboard (an old ASUS A8N-VM CSM) actually didn't report all 4GB until I changed the "memory hole" setting. @Ignacio – oKtosiTe Mar 10 '11 at 20:19

There should be 4 GB available, minus any reserved for an integrated graphics card (if you have one). Some is set aside for DMI for USB and PCI Express, but that's relatively minuscule.

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As much as the chipset and BIOS let you have; anywhere between 3.2 and 4GB.

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Can be even lower. On one of my systems, the BIOS/chipset doesn't allow remapping of the RAM overlapping with addresses that is used for IO. The system properties explicitly state 4.00 GB (2.94 GB usable). Yes, that is on Win7 x64. – Steven Don Mar 11 '11 at 9:51

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