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I have recently installed 4Gb of ram for an existing 12.04 32bit Ubuntu. It's not being recognised, only 3.2Gb is showing, See:

administrator@Root2:~$ free
             total       used       free     shared    buffers     cached
Mem:       3355256    1251112    2104144          0      48664     391972
-/+ buffers/cache:     810476    2544780

System is PAE capable, See:

administrator@Root2:~$ grep --color=always -i PAE /proc/cpuinfo
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts

The system us fully patched and tried to run manual PAE upgrade, See:

administrator@Root2:~$ sudo apt-get install linux-generic-pae linux-headers-generic-pae
[sudo] password for administrator: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
linux-generic-pae is already the newest version.
linux-headers-generic-pae is already the newest version.
The following packages were automatically installed and are no longer required:
  language-pack-zh-hans language-pack-kde-en language-pack-kde-zh-hans
  language-pack-kde-en-base kde-l10n-engb kde-l10n-zhcn
  language-pack-zh-hans-base firefox-locale-zh-hans
  language-pack-kde-zh-hans-base
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

I am not sure what else to try to recognise the full physical memory installed other than loading 64bit. Any thoughts? Thanks!

output of uname -r

administrator@Root2:~$ uname -r
3.2.0-24-generic-pae
share|improve this question
    
Looks correct to me. You'll need 64 bit. IIRC each single process is limited to 3 Gb under 32bit, so that's why you see that. –  gecko May 9 '12 at 19:17
1  
I don't think the per-process memory limitation is the problem. It looks to me like, for some reason, the PAE kernel is not actually running. Have you checked to see if it is? Can you add the output of uname -r to your question? –  Eliah Kagan May 9 '12 at 19:23
    
@ Eliah: Yea, you're right, I missed that he's looking at total ram installed, not per process. –  gecko May 9 '12 at 19:31
    
@Eliah Kagan See output or the current version: administrator@Root2:~$ uname -r 3.2.0-24-generic-pae –  David May 9 '12 at 19:42
    
@gecko, free reports system memory, not its own memory. It looks like a problem with the motherboard. Check the output of dmesg or the contents of /var/log/kern.log and look for the section with the e820 memory map and add that info to the question. –  psusi May 10 '12 at 1:27

3 Answers 3

@fossfreedom - Problem has been fixed by upgrading the BIOS to the most recent one. Thanks for the hint! See available memory output after the change:

administrator@Root2:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          4026       1105       2921          0         45        311
-/+ buffers/cache:        748       3278
share|improve this answer

Even if you were running windows you wouldn't see the entire 4gb of memory allocated. Part of it is reserved for Graphics Ram. If you go to the Manufacturer website and look at the technical specs for your system under memory it will tell you how much of the installed memory is usable.

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32Bits only goes till 3.2GB of ram. You should upgrade to 64-Bit if you want to take the full advantage of your memory

share|improve this answer
    
He can use more than 3 Gb, just not in a single process. :-) –  gecko May 9 '12 at 19:19
5  
This answer is incorrect. The 32-bit memory limitation is overcome by running the PAE kernel, which lets you access up to 64 GiB of RAM. See en.wikipedia.org/wiki/Physical_address_extension#Linux. The question is about why that's not working. (Sorry, didn't actually mean to downvote though, have undownvoted.) –  Eliah Kagan May 9 '12 at 19:20
    
This answer is incorrect so accepting it is giving the wrong signal. –  Rinzwind May 9 '12 at 20:01
    
@Robert Hollander : Yes I will upgrade it to 64bit to get it working. Obviously I tried to avoid doing it but there does not seem to be an alternative unfortunately. Thanks all for the input! Much appreciated! –  David May 9 '12 at 20:03
1  
@David - what is your computer (make and model) - add this to your question. e.g. maybe a BIOS issue as per this Q&A? askubuntu.com/questions/80721/… –  fossfreedom May 9 '12 at 20:29

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