I upgraded 2gb memory to 4gb on Lifebook 6025. I followed instructions for pae to recognize the 4gb by doing

  1. sudo apt-get install linux-headers-server linux-image-server linux-server

  2. edit grub by adding forcepae -- forcepae

  3. reboot

But still it shows the same as before with 3.2gb as below.

jmin@jmin-LifeBook-A6025:~$ free -h
             total       used       free     shared    buffers     cached
Mem:          3.2G       966M       2.3G        60M        51M       530M
-/+ buffers/cache:       384M       2.8G
Swap:         3.9G         0B       3.9G
jmin@jmin-LifeBook-A6025:~$ dmesg | grep -i pae
[    0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-74-generic root=UUID=2fca00b1-5199-4d2d-bb5f-9728c10d7a05 ro quiet splash forcepae -- forcepae vt.handoff=7
[    0.004596] PAE forced!
[    0.008000] PAE forced!

What am I doing wrong? How can I make it use all 4GB memory? Thank you.

  • The rest is used by the video adapter. – Pilot6 Jan 15 '16 at 18:19
  • Thank you. But shouldn't the total say 4.0G instead of 3.2G? – user1026669 Jan 15 '16 at 18:20
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    @Pilot6 is correct. Free shows the usable RAM. Video RAM and generally "locked" kernel memory is not accounted. I have 16G and free says total 14G. You system is ok and using all the RAM. – Rmano Jan 15 '16 at 18:49
  • Thank you for the comment. Please see my comments below. BTW, before I added the 2g memory, it had 2g memory and I think the free -h showed the total 2g, not like 1.4g for the totals. Why is it that way? Thank you. – user1026669 Jan 15 '16 at 21:12

Part of the memory is allocated to the on-board Video card. You may be able to adjust the amount of memory the card can use, in the system BIOS, but you will never see the full 4GB, as the video card must be allocated some amount. You could theoretically disable on-board video if your BIOS allows it, but then your system would have no video, as it's a laptop.

You do not need to force PAE to on. Ubuntu now only supports PAE for 32-bit Intel systems. So forcepae doesn't actually do anything, but give you some extra messages in the log about it being forced.

Installing the linux-image-server packages was also not necessary. You only seeing 3.2GB vs 4GB, is unrelated.

On my system, with Intel video, I have 32GB of RAM installed, which is 33554432 kilobytes, while free shows I have 31860640 kB total, which is 30.39 GB. Some of that difference is the allocated video memory, and some of that difference is the kernel memory.

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  • Thank you for your comment. Actually even before installing pae as I did, the free -h shows 3.2g. And I thought due to the lack of the pae, it shows 3.2 not 4.0g. So, I installed for pae as shown above, but then still the same. Did I need to install pae at all on Ubuntu 14.04 version, or is the pae already included? BTW, I have fedora21 desktop with 8g ram, and free -m shows 7981, which is close to 8gb ram. Does it mean that ubuntu and fedora shows different totals for the memory size? Or is that because fedora21 video has its own memory, not using the system memory? Thank you very much. – user1026669 Jan 15 '16 at 21:10
  • I just looked at my fedora21 video memory by doing 'lspci -v -s 01:00.0 ' and it shows 256M prefetchable. Is that why the 'free -h' on the fedora21 shows near 8g ram because the video card does not use system memory? Is that because the laptop video card does not have its own memory and borrows from the system memory unlike the fedora21 desktop? Thank you very much. – user1026669 Jan 15 '16 at 21:24
  • PAE is on by default. If your hardware doesn't support PAE, Ubuntu 14.04 won't even boot. – dobey Jan 15 '16 at 21:29
  • Right, if you have a discrete video card on your workstation PC, like an NVidia card, it has memory on the card, and it is not shared with the system RAM. The laptop graphics are part of the CPU, and it shares memory with the system RAM, which means available system RAM appears as less that what you have installed. – dobey Jan 15 '16 at 21:30
  • dobey, thank you very much. One last question. I think I saw 2g for the total when I did 'free -h' on the a6025 laptop before I installed 2 modules of 2g memory to make the total of 4g memory. Shouldn't it have shown something like 1.4g instead of 2g? How can that be explained? Or did I see that incorrectly, I mean it was not 2g that I saw? Thank you. – user1026669 Jan 15 '16 at 22:12

To address more than 3GB of RAM using PAE on Intel-based systems, you must have support from the chipset. The Intel 945 and older chipsets for example don't support this.

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Unfortunately, a 32 bit operating system can only address 4GB of memory. Your swap space and graphic memory space will be included in this address block, so you might only be able to see 3.2GB memory; if this is insufficient, I'd recommend using the x64 version of 14.04. I've had no problems with compatibility.

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  • Thank you for your comment. For now the a6025 cpu is , I think, for 32bit. So, 64bit OS is out of the question. So, there is no way to get all 4g? – user1026669 Jan 15 '16 at 18:19
  • This is not quite true. 32-bit non-PAE can only address up to 4GB of memory. However, Ubuntu 14.04 only supports PAE-enabled 32-bit systems, so any 32-bit system running 14.04 can address more than 4GB. However, if you only have 4GB, you obviously can't address more than 4GB, no matter what architecture you're on. :) – dobey Jan 15 '16 at 18:55
  • dobey, thank you for your comment. If 14.04 has only pae-enabled 32bit OS version, I did not have to install pae by doing "sudo apt-get install linux-headers-server linux-image-server linux-server". Is this true? Thank you. – user1026669 Jan 15 '16 at 21:16
  • @user1026669 Yes, as described in my answer, that was unnecessary. – dobey Jan 15 '16 at 21:38
  • dobey, thank you very much. Can I undo what I did then? Is there any damage to be done to the laptop? Thank you. – user1026669 Jan 15 '16 at 22:10

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