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How do I check my whether my Ubuntu is 32-bit or 64-bit and whether or not it is using full RAM? I'm concerned that because my system is 32-bit it isn't using the maximum OS-supported RAM. It says my PC has 8GB RAM, but how do I verify it is using or detecting this as 8GB RAM?

Regarding Sotanaht's answer: the System Tab shows Release 11.04 (natty), Kernel linux 2.6.38-11-generic-pae, Gnome 2.32.1 .

Follow up:

After finding my answer. Because I have 8GB hardware RAM, I don't want to be restricted to 4GB RAM, therefore removing my 32-bit Ubuntu 11.04, and downloading 64-bit Ubuntu 11.04 (so that my applications can utilize full hardware RAM too, specially for 3D animation rendering, image processing, video editing)

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On of the issues with the 64 bit version has been the Adobe Flash plugin. I am using the latest version on my 64bit system with no problems. –  peck Sep 23 '11 at 1:19

5 Answers 5

up vote 7 down vote accepted

PAE means your kernel is 32-bit but it's configured to use Physical Address Extension so the whole OS can use all your physical memory. The limitation of PAE, however, is that no application alone can use more than 4Gb of memory.

See the wikipedia article for more technical details

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How do i make my application,system to use 8GB full when they need it? Instead of 4GB limitation? Is there already 64-Bit Ubuntu 11.04 to use? Will be the package manager apt-get be same as 32-Bit? –  YumYumYum Sep 14 '11 at 6:47
Yes, you'll need to make a fresh install of 64-bit Ubuntu. It's pretty much identical in its appearance to the 32-bit one, all programs are the same. There are some proprietary programs (Flash) which may be slightly trickier to make working but nothing dramatic. I'm not sure if you can upgrade 32-bit to 64-bit - may be worth asking a separate question –  Sergey Sep 14 '11 at 8:00

In a terminal type free -to.

Quick and easy.

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To deal with the requirement for GB or MB display, I'd add the m flag (for megabytes) : free -tom –  belacq Sep 14 '11 at 15:32
Always something to learn isn't there? –  peck Sep 23 '11 at 1:08

If you open System Monitor (System > Administration > System Monitor) and go to the "System" tab, the number after "Memory" should correctly display your computer's ram in GB

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There it shows 7.8GiB. Does this mean i am running 8GB successfully? All my applications can also now use that memory. Or 32-bit will show 8GB but not use it? –  YumYumYum Sep 13 '11 at 22:54
System tab it also shows > Release 11.04 (natty), Kernel linux 2.6.38-11-generic-pae, Gnome 2.32.1 –  YumYumYum Sep 13 '11 at 22:58
Yes it means that you are "running 8GB successfully" –  AmanicA Sep 20 '11 at 14:39

Sergey is right that PAE means you're running a 32-bit version. Another very easy way to see what version you have is to open a terminal window and type:

uname -a

In my case it returns:

~$ uname -a

So the kernel is 2.6.38-11-generic, and the version of Ubuntu is x86_64 (or 64-bit).

However, a great way to get all sorts of information is to install System Profiler and Benchmark. It's in the Ubuntu Software Center and will likely become one of your favorite ways to get information about you system. Just install it, open it, and you'll know how to use it; it's obvious and intuitive so you won't need instruction.

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To display the current memory usage of your system, use the following command in the terminal [ctrl+Alt+T]

free -m 
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It would be helpful if you provided more information to the OP. –  Kevin Bowen Mar 21 '13 at 9:13

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