I have 4 GB of RAM installed, but why are only 2 GB are usable?

Question

In the BIOS it says 4096 MB, so the BIOS detects it. However, Windows 7 only lets me use 2048 MB. What's the problem?

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score 8 · Accepted Answer · edited Dec 28 '17 at 13:34

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Use MSConfig → Boot → Advanced.

Is the box 'Maximum Memory' checked?

edited Dec 28 '17 at 13:34

Peter Mortensen

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answered Aug 27 '09 at 02:10

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Someone has been playing without knowing what they are doing if this was set... – gbn Aug 27 '09 at 04:40
It's unchecked by default, at least on my install... – atom255 Sep 02 '09 at 16:36
this didnt work for windows 7 starter 32 bit :( – Aquarius Power Jul 17 '17 at 20:12

score 2 · Answer 2 · answered Aug 27 '09 at 07:36

It's because Microsoft intentionally made this software limitation - 4GB memory - under 32-bit Windows Vista/7. This is a way to upsell the more expensive 64-bit OS.

This post has all the details. Licensed Memory in Windows Vista:

I say the restriction to 4GB is a licensing issue because that’s how Microsoft’s programmers evidently have thought of it. The 4GB limit is retrieved from the registry by calling a function named ZwQueryLicenseValue, which is itself called from an internal procedure which Microsoft’s published symbol files name as MxMemoryLicense. If you remove this check for the licensed memory limit then a restriction to 4GB is demonstrably not enforced by other means. Yet I must admit that I have not found where Microsoft says directly that 32-bit Windows Vista is limited to 4GB only by licensing. The supposed License Agreement doesn’t even mention the word memory. What, really, is going on?

score 1 · Answer 3 · answered Aug 27 '09 at 02:02

Ah, I see you have a Dell. Mine is similar -- a 4GB Dimension 5150 system that only reports 3.3GB as installed, all of it usable. This was the case under Vista-32, Windows7-64, and assorted Linux distributions of both bitness-es.

In my case, this is a limit of the chipset -- the onboard video appears to sit on a large part of mappable memory, making it unusable to the OS.

score 1 · Answer 4 · edited Dec 28 '17 at 13:48

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My guess is that it is a mixture of 32 bit which takes you down to ~3.5 GB, and then the rest is being taken up by on board graphics, but to be honest, 1 GB+ of video RAM does seem like a lot.

Do you have a load of PCI / add ons to your pc? These may be eating up the addressable resources.

edited Dec 28 '17 at 13:48

Peter Mortensen

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answered Aug 27 '09 at 02:04

William Hilsum

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No I dont. Let me reboot right now and check for u. – ctzdev Aug 27 '09 at 02:09
i doubt that, Windows then would only report ~3.5GB and not the full 4 GB. – Aug 27 '09 at 02:16

score 0 · Answer 5 · edited Dec 28 '17 at 13:49

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That is caused by a few things. x86 can only detect a TOTAL of 4 GB, and that includes your graphics card and other stuff too. Just go to 64 bit.

edited Dec 28 '17 at 13:49

Peter Mortensen

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answered Nov 06 '14 at 21:01

musio

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Nope. x86 can detect way more. It is not an x86 limitation. (Example: x86 with PEA enabled). Using a 64 bit OS is sensible though and recommended when you have 512MB or more. (it offers advantages way before you hit the 4GB limit). – Hennes Nov 06 '14 at 21:05
@Hennes: PEA? Do you mean [PAE](https://en.wikipedia.org/wiki/Physical_Address_Extension) (*Physical Address Extension*)? – Peter Mortensen Dec 28 '17 at 13:53
Yes, its 'teh' typo. – Hennes Dec 29 '17 at 15:26

I have 4 GB of RAM installed, but why are only 2 GB are usable?

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