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I recently installed Ubuntu 11.10 x86 on a new computer that has 2 x 4 GB RAM installed (8 GB total).

But when I go to the Ubuntu system monitor it only shows 3.4 GB of memory (and 8 GB swap). I also have a Windows 7 installed with dual boot on the same computer, and there it shows 8 GB RAM in "Control Panel > System". The BIOS also recognize the 8 GBs.

I thought this could be a problem of the x86 release, and I needed to use x64, but I just asked a friend that has the same computer with Ubuntu 11.04 x86 and he says the system monitor shows him 8 GB of RAM.

What could I try to get Ubuntu to recognize the 8 GB of RAM? I really don't even know where to start testing.

$ sudo dmidecode --type 17 | grep -E "Size|Form Factor|Memory Device|Type"[sudo] password for revered:
Memory Device
    Size: 4096 MB
    Form Factor: DIMM
    Type: Unknown
    Type Detail: None
Memory Device
    Size: 4096 MB
    Form Factor: DIMM
    Type: Unknown
    Type Detail: None
Memory Device
    Size: No Module Installed
    Form Factor: DIMM
    Type: Unknown
    Type Detail: None
Memory Device
    Size: No Module Installed
    Form Factor: DIMM
    Type: Unknown
    Type Detail: None

$ free
             total       used       free     shared    buffers     cached
Mem:       3608164     566356    3041808          0      36748     222304
-/+ buffers/cache:     307304    3300860
Swap:      8369148          0    8369148
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2 Answers 2

up vote 5 down vote accepted

On a 32-bit operating system, there's a maximum of 4GB of RAM which can be used. The exception is a PAE kernel, which is basically a 32-bit kernel which supports more RAM.

I suggest you just install a 64-bit operating system, as this generally gives better performance. The other solution would be to install the PAE kernel, which can be done from the software centre.

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I guess I will just download 11.04 and test that, I'm not liking 11.10 very much even after customizing it to make it look like the old v10. –  Uoplem Dec 25 '11 at 19:46
2  
You probably use the generic kernel which would't recognize more then 4GB. Can you post the output of uname -a to verify that. –  mikewhatever Dec 25 '11 at 20:53
    
@mikewhatever Linux user 3.0.0-12-generic #20-Ubuntu SMP Fri Oct 7 14:50:42 UTC 2011 i686 i686 i386 GNU/Linux –  Uoplem Dec 25 '11 at 21:01
4  
Yep. Just install linux-image-generic-pae and reboot. The PAE kernel should see all the RAM. –  mikewhatever Dec 25 '11 at 21:21
    
The limit for a 32-bit OS without PAE is 4 GB, not 8 GB. –  Jesper Dec 26 '11 at 18:32
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The PAE kernel gets installed by default if the 32bit installer detects 4GB or RAM or more. Something must have gone wrong with that detection or you may have had less RAM at the time of installation, and upgraded later.

Regardless, you should use the PAE kernel which will see all the RAM. Install the linux-image-generic-pae package which should pull in the latest PAE kernel, and if all goes well, remove the generic kernels.

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I guess the click I did on the "skip" button could be the reason, I installed 11.04 now which has the normal gnome by default to choose at login, I think ill stick with this one. –  Uoplem Dec 26 '11 at 16:58
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