Hey fellow LINUX heads....
I recently upgraded my RAM from 2 2gb sticks to 4 2gb sticks=8gb.
I have a Gigabyte mobo...GA-MA78GM-US2H, says it supports up to 16gb RAM and bios DOES reflect that I have 8gb installed.
However, when I cat /proc/meminfo these are the first two lines....
MemTotal: 3354744 kB
MemFree: 2776292 kB
saying Mint is using only about 3 gb, right? Any ideas to what's wrong?

Are you using 32bit? The 32bit address limit is about 3.5GB(effective). You can switch to a PAE kernel or switch to 64bit.

Thanks Laslow,

I had just found online where this is true. A guy at the Micro Center told me 32bit operating systems can have up to 32 or 64 gigs of RAM, apparently he was wrong. (it's okay, I still love you Micro Center!).

I am downloading 64 bit debian and centos as I type, what 64 bit version would you suggest?

Choosing a distro is a little like choosing underwear. It all depends on how it fits you. That being said, I use Centos 64bit (32bit on older machines). There is certainly nothing wrong with Debian either.

Lazlow, thank you for sharing your underwear.

Either you are not using a PAE kernel, or you have a BIOS setting wrong.

If you aren't using a PAE kernel, the easiest solution is to switch to one. Reinstalling the 64-bit build of your distribution might be better, but it is certainly harder.

If you have a BIOS setting wrong, a 64 bit Linux would make no difference. For either PAE or 64 bit to see the memory, you need the BIOS to map the memory correctly.

So first find out if it is a BIOS problem. If it hasn't been so long since the last boot that the dmesg log has overflowed, you can find the physical RAM map by
On one of my systems, it looks like this.
Notice the last line of mine. It shows the ram mapped above 4GB (0000000100000000 represents 4GB). If you have no ram mapped above 4GB, the BIOS has some setting incorrect and no OS can use more than 3 point something GB of ram.

The guy at Micro Center got that right (very impressive. That's way beyond the knowledge you would expect for someone working in a computer store.)

I expect your existing distribution has a package for a PAE kernel you can download and install. Doing so would be much simpler than reinstalling the whole distribution.

In your other thread, someone said Mint has 64 bit (it's been long enough since I tried Mint, I wasn't sure, but I think the Mint I tried was 64 bit). So why are you switching from Mint?

Anyway, Centos would be a poor choice. Stick with some Debian based distribution (Mint, or Mepis, or Ubuntu or Debian itself).

Once a beginner is used to Mint, switching to a distribution in the Red Hat family would have lots of confusing differences for no benefit.

Even more significant, Centos is a server distribution. I've installed Centos a few times and I use it at work. Its install process very much assumes you are setting up an enterprise server rather than a home system.

An experience Linux user can blast right past the Debian vs. Red Hat differences and past any assumptions made by the installer, and configure almost any Linux distribution into whatever he wants.

But a beginner is just going to follow the flow laid out by whoever put together the distribution and would get totally lost trying to reach a Home Linux system from the Centos installer.

Or you have a CPU that does not support PAE

Read the first post.

So the CPU does support PAE.

In the first post he says that the bios has recognized the entire 8gb, so I really doubt this is a bios issue.

As far as Centos being a poor choice, I would disagree with that. The install setup is virtually identical to Fedora's (C5 was based on FC6) and very few people would call Fedora a "sever only" distro.

There is a version of Mint for 64-bit architecture: it's listed as "amd-64" but, as we all know, that's just shorthand, if you're using an Intel CPU, folks. It's supposed to be friendly even to the Core 2 Duo family, as rumour would have it.

Apparently it started two versions ago, but see this thread if you want the details:
http://www.linuxmint.com/blog/?p=389.

Hope this helps.

Look at a bunch of the similar threads in LQ (threads where the initial issue is that Linux doesn't see all the ram). You should find several in which the problem is discovered to be some BIOS setting (OS install mode, or disable memory remap, etc.). Then notice that before the BIOS setting was corrected, the BIOS was seeing all the ram and reporting it to the user at boot time, but not reporting it to Linux in the physical memory map.

I'm not guessing whether the problem is in the BIOS (vs. a non PAE 32 bit kernel). There is no need to guess, because you can check in dmesg and find out for sure.

johnsfine

If you look, the very few threads that do actually involve a bios issues with greater than 4gb ram were 1st generation boards. 1st generation boards did not support 2Gb sticks.