Hi

Just installed CentOS 6.2 (32 bit) on a PC with 4GB ram but it only recognizes 3.36GB. Now I read about PAE which is in older CentOS versions enabling the system to use more physical RAM.

The question is how do I make the installation recognize and utilize the entire 4GB?

dmidecode shows 4GB

Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 4 GB
Error Information Handle: Not Provided
Number Of Devices: 4

[root# cat /etc/redhat-release
CentOS release 6.2 (Final)
[root# uname -a
Linux *** 2.6.32-220.23.1.el6.i686 #1 SMP Mon Jun 18 16:56:21 BST 2012 i686 i686 i386 GNU/Linux


Rgds
Mburu

I haven't used CentOS 6 myself, so I don't know for sure, but do you have some reason for saying "older versions"? Do you think CentOS 6.2 doesn't offer a PAE kernel?

The PAE kernel should be a package you can install with Yum.

dmidecode can see and report ram even if the motherboard can't really use that much ram.

Typically that phrase is a lie. If the motherboard is limited to 3 and a small fraction GB, it typically reports the max capacity as 4GB.

So maybe a PAE kernel will make no difference (if so, a 64 bit kernel also wouldn't change the 3.36GB limit).

Installing the PAE kernel may be the easiest way to find out whether the motherboard is responsible for the 3.36GB limit.

But you could also find out whether PAE would help before installing that kernel. See my other posts on this topic, such as:

http://www.linuxquestions.org/questi...5/#post4471420

By previous versions I mean like CentOS 5.8 in which "yum install kernel-pae" is available but not in 6.2

I have physically asserted the RAM is 4GB plus below is my lshw output on memory

That is the same dmidecode info, simply reported by a different tool. The BIOS also uses that same dmi info when reporting installed memory.

None of that tells you whether the motherboard actually supports that much memory. If the max ram supported by the motherboard is 3.36GB, that means you can plug in 4GB and dmi info will tell you that you have 4GB, and the BIOS will tell you there is 4GB, but the BIOS will tell the OS there is only 3.36GB.

If the PAE kernel is harder to get for Centos 6, that is an extra reason to use the dmesg method I described in other threads to find out whether PAE would do any good.

Edit: I just did a google search "centos 6" "pae kernel" and the answer seems to be that Centos has not dropped the PAE kernel, it has dropped the non PAE kernel, so the one you already have is probably PAE.

It is possible there is a BIOS menu choice (often called memory remap enable) to allow more than 3.36GB to be used. But it is likely a hardware restriction of the motherboard and you are stuck with the 3.36GB limit.

Please post the output of If it shows that you already have PAE enabled then there are two possibilities:
1. This is a hardware limitation that usually is found on mainboards that support a maximum of 4GB RAM and therefore don't offer memory remapping.
2. Your hardware can support more than 4GB of RAM, but memory remapping is disabled in the BIOS.

True 6.2 is pae enabled by default,,,,,

@TobiSGD

http://www.centos.org/modules/newbb/...ime=1341839130

At least we agree.

Would this mainboard have integrated graphics ?
Check your BIOS.

Seems I have to investigate the motherboard itesf or forget the 4Gb all together.