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Possible Duplicate:
Windows 7 64-bit is only using 3 GB out of 4 GB

My HP HDX 16 laptop has 4GB of ram and runs a 64-bit system. I always go into Dxdiag for some reason and i always see it says 4096 MB of RAM. But today I felt the PC was misbehaving, so i opened it and it said 3128 MB of RAM. Where did that 1 GB go??

When I check the computer properties, it says I'm using a 64-bit system with 4.00GB of RAM, but why does everything else say it has 3?

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marked as duplicate by Sathya May 31 '12 at 16:32

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

If you run a program like CPU-Z what does it report for each of the memory banks? – Scott Chamberlain May 31 '12 at 14:28
up vote 7 down vote accepted

The most likely reason is due to the video memory set on your BIOS. Probably it is set to dynamic and it auto-adjusted to 1GB due to some video-heavy application that you run. Check on your BIOS settings.

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Here is the same situation with the user and he asked it on Microsoft.

Significant chunks of address space below 4GB (the highest address accessible via 32-bit) get reserved for use by system hardware:
• BIOS – including ACPI and legacy video support
• PCI bus including bridges etc.
• PCI Express support will reserve at least 256MB, up to 768MB depending on graphics card installed memory.

What this means is a typical system may see between ~256MB and 1GB of address space below 4GB reserved for hardware use that the OS cannot access. Intel chipset specs are pretty good at explaining what address ranges gets reserved by default and in some cases call out that 1.5GB is always reserved and thus inaccessible to Windows.

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The author is using a 64-bit operating system. – Ramhound May 31 '12 at 16:04
@Ramhound in the post user also running the 64bit of version. – avirk May 31 '12 at 16:07
Which leads me to wonder the reason you bring up the typical limits of a 32-bit Windows operating system. – Ramhound Jun 28 '12 at 17:45

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