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4 GB of Ram installed but only 2.97GB usable. What gives?

I got a Dell laptop with Windows 7 Professional. Initially it had 3GB of RAM. Then I upgraded my laptop increasing RAM up to 4GB.

Viewing system details through My Computer icon it is saying that the laptop has got 4GB of memory (BIOS shows the same thing), usable 2.96 GB. According to the task manager my laptop has got only 3GB of memory.

When the RAM consumption reaches > 2GB, Windows shows a pop-up on the screen saying that I am running out of memory. I used to get the same pop up window having 3 GB of RAM.

Why is my RAM is not fully exploited?

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What OS version are you using. It's most likely that you are running an x86 (32bit) build hence the ~3 gb limit –  IUnknown Jan 27 '12 at 15:04
    
It could be that motherboard can't address all RAM due to chip configuration. Make sure that the RAM is actually supported by your computer (this can happen even in 64bit operating systems). –  AndrejaKo Jan 27 '12 at 15:04
    
Related: superuser.com/questions/67444/… - 32Bit processors can address more than 4GB of RAM with PAE which is not available in the desktop versions of Windows (though it is available in the server versions of Windows). –  Nathan Adams Jan 27 '12 at 17:43
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marked as duplicate by studiohack Jan 27 '12 at 17:29

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3 Answers

up vote 7 down vote accepted

You're running a 32bit version of Windows and/or your graphics processor reserves some of your system memory for itself.

edit: I just realized, our very own Jeff Atwood wrote an article about exactly this issue.

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What does this mean with 32bit? A 32bit cpu may address 4gb of ram without any problems. Surely, a GPU (or what else do you mean?) won't initially address 1gb if you aren't doing anything. The GPU does have its own caches. –  Michael Jan 27 '12 at 17:13
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@Michael, yes it can address 4GB of space, but much of this address space is dedicated to Memmory-Mapped I/O. en.wikipedia.org/wiki/Memory-mapped_I/O –  user606723 Jan 27 '12 at 17:21
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And that was almost 5 years ago. –  Daniel Beck Jan 27 '12 at 17:39
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You are probably running windows 7 32 bit version, which can't address more than ~3.3 GB at a time.

Upgrading to win7 64bit would solve this problem.

Another possibility is that your GPU reserves memory or your BIOS doesn't detect your additional stick, you can check that in your BIOS.

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Correct, it is 32 bit OS. –  ucas Jan 27 '12 at 15:11
    
@ucas then mark my answer as accepted, after that go and install the 64bit version to get your missing 1GB of RAM. –  bamboon Jan 27 '12 at 15:14
    
You want to make sure that your processor is a 64-bit processor; if it isn't then having a 64-bit OS will do you no good. –  Kevin M Jan 27 '12 at 15:22
    
@KevinM you think, there are notebooks out there which have 3GB of RAM and don't have 64bit cpu? –  bamboon Jan 27 '12 at 15:33
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32bit Windows 7 will use 32bit addressing thus all device memory space will be retracted from real 4GB memory. Windows server editions and 64bit editions will get closer to installed memory. Why? Because page list would take a lot of space and there is no gain trying to address >3,5GB. because gained space will be wasted by memory management.

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