I have 64Bit Ubuntu installed, and a MSI Graphics card.
Any ideas on why this might be happening?
Check in the motherboard BIOS for an option similar to "map around memory hole." Your motherboard's chipset may not support this option.
Older, especially laptop, chipsets (for example, the Intel 945p chipset) did not support true 64 bit memory addressing and had a ceiling of 4GB even in 64 bit mode. If that is the case with your system then this is a hardware limitation that can't be addressed without replacing the chipset (motherboard.)
Is it an integrated VGA? In that case, some will share the main memory, so it won't be available to applications.
Is the missing memory on the graphics card or memory in your computer? How have you determined that only 3.2GBs are showing up?
If it's a matter of available memory, you might check System Monitor (in System Settings) and look under the Processes tab, and then click "Memory" to put the processes in order so you can easily see which are using the most memory. The Resources tab will show total memory in your system, as well as how much is being used.
You need to install pae kernel. This will allow usage of memory on a computer larger than 4GB
Most times you can install with:
sudo apt-get install linux-generic-pae
Once you restart you should see the correct memory size.
uname -a
andfree -m
here. Both of these commands are run in the terminal which you can open by doingctrl+alt+t