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Does Ubuntu Desktop 32 Bit support more than 4GB memory WITHOUT changing anything (Without having to activate PAE via compiling kernel or anything similar). Will installing the 32 Bit Ubuntu on the machine be enough to detect the additional memory automatically. If yes, will this work if I add more than 4GB with a 32Bit Ubuntu already with 4GB Ram.
One example would be to have 8GB Ram with Ubuntu 32 Desktop.

My Motherboard supports up to 8GB RAM and it has 32 Bit and 64 Bit support (It is the intel DP35DP)

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There was the issue which I posted in launchpad about the LiveCD/LiveUSB that when installing from them you would get a black screen if you had a integrated video card and an Nvidia card. The solution was to disconnect/connect the VGA or HDMI cable from the Nvidia card. At least until a solution appeared. The other one was at least 4 system freeze appeared to me on the 64bit one. I know this would be solved in a couple of weeks but for the time I would use the 32bit until I test again when 12.04.1 comes out. –  Luis Apr 30 '12 at 1:43

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Ubuntu 10.04 and newer should support PAE out of the box, and most processors produced in the last twelve years do too, so in theory it should work fine.
If you're trying to install Karmic or older, you may need to enable PAE yourself, as per this wiki article.

It may also be necessary to switch certain options in your BIOS, such as "Software Memory Hole".

The information in this wiki article may be of use to you as well:

A 32-bit computer has a word size of 32 bits, this limits the memory theoretically to 4GB. This barrier has been extended through the use of 'Physical Address Extension' (or PAE) which increases the limit to 64GB although the memory access above 4GB will be slightly slower.

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So if i install Ubuntu 32bit on my 4GB computer. Then put in another 4GB for a 8GB total. It will read it without chaging ANYTHING at all. –  Luis Jan 4 '11 at 19:01
    
You should at least check which kernel you're running first, by issuing the command uname -a. I'm pretty sure PAE would be needed to use the whole 4 GB in the first place. @CYREX –  oKtosiTe Jan 4 '11 at 19:14
    
I have 4GB right now and i just installed the ubuntu desktop 32bit normal one found on the website. When i cat proc/meminfo i get the total like this MemTotal: 4054012 kB The cpu shows pae when i do this: cat /proc/cpuinfo | grep pae –  Luis Jan 4 '11 at 21:46
    
Your kernel needs to support it too. Does the name of the kernel as shown in uname -a include anything like PAE or bigmem? @CYREX –  oKtosiTe Jan 4 '11 at 23:11
    
As Scaine commented on one of the other answers, you could check with System > Administration > System Monitor. Even if it's not in the kernel's name, it may still be supported. @CYREX –  oKtosiTe Jan 5 '11 at 20:41

As in Ubuntu documentation:

  • Ubuntu 12.10 (Quantal) and onwards: The generic default kernel already has PAE enabled.
  • Ubuntu 10.04 LTS (Lucid Lynx) to Ubuntu 12.04 LTS (Precise): Both the CD and DVD installer of Ubuntu automatically installs the PAE enabled kernel if it detects more than 3 Gb of available memory. In the case of the liveCD, a working network connection is required, since the PAE enabled kernel packages are not present on the CD.

reference: https://help.ubuntu.com/community/EnablingPAE

So you don't have to install kernel or compile it. Just use the alternate installer CD; or Ensure you are connected to interent while installing if you prefer the live desktop CD

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PAE above is the best route. For your information, This week I took advantage of cheaper UK 8Gb RAM (£20.00!) modules for my current AMD X2 Dual core with 4Gb DDR3 (1333) memory, replacing the 2 modules with one single 8Gb, but found then I only had some 3.7Gb in memory using (the System Tool). A quick read here on askubuntu and the said above article https://help.ubuntu.com/community/EnablingPAE using PAE, a quick install via Terminal, and a reboot, then gave me 8Gb.

For the present, I'm only running 11.04 on 1 of 3 comps (others run 12.04), but will upgrade to the latest when time prevails. I merely wanted the memory to work now and PAE was not installed on my 11.04. It took me as long as it takes to download via Terminal as in the above help "Enabling PAE manually" section of the article. If PAE supports upto 64Gb as it says, then I'll take the 16Gb RAM route.

I suggest anyone looking to upgrade similar at 11.04 stage, follow the above.

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pae-kernel is default in 12.04, so you could use up to 64 gig (if your motherboard allows that ;-)

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If you use the PAE enabled kernel, then yes. I am using 32-bit with 8GB of RAM right now. I think PAE was also made the default for 12.04.

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Yes, and as an aside, if you install 32-bit on a system with 4 GB it should automatically install the PAE kernel for you. –  roadmr Apr 29 '12 at 23:20
    
@dobey - It looks like my v12.04 LTS also installed with PAE support by default (uname -a). –  jjwdesign Jan 6 at 21:42

From the Ubuntu Community Documentation: Enabling PAE

Both the CD and DVD installer of Ubuntu 10.04 automatically installs the PAE enabled kernel if it detects more than 3 Gb of available memory. In the case of the liveCD, a working network connection is required, since the PAE enabled kernel packages are not present on the CD.

Physical Address Extension (PAE) is a feature that allows x86 (32-bit) processors to access a physical address space (including random access memory and memory mapped devices) larger than 4 GB (theoretically upto 64GB).

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And I installed 32-bit 10.10 on a server with 4Gb of RAM two days ago. Didn't have to do anything - it just worked. If you run system/administration/system monitor after your install, you can check the "system" tab to confirm that the pae kernel auto-installed. –  Scaine Jan 5 '11 at 0:20

if you installing ubuntu 32bit with 4gb, it will detect automatically, and installing linux kernal pae. so you can use your 4gb ram

but if you upgrade to 4gb ram, you need to install linux kernel PAE.

this is a good link : https://help.ubuntu.com/community/EnablingPAE

:D

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