Optiflex FX160 memory limit

Hello,

I'm trying to figure out why the dell optiflex fx160 only shows 3GB RAM, even when running a 64-bit OS.

Is this a hard limit of the chipset? Would a BIOS update maybe help?

The specifications say that 4GB is supported so I would assume there is some way to get it to work?( https://www.dell.com/downloads/global/solutions/Optiplex_FX160_Customer_Brochure_English.pdf

(Below follows some output to verify that it's really only seeing 3GB and really is a 64-bit OS and what CPU it has.)

coolfire@n01:~$ cat /proc/cpuinfo | grep "Intel(R)" | head -1
model name : Intel(R) Atom(TM) CPU 330 @ 1.60GHz
coolfire@n01:~$ free -m
total used free shared buff/cache available
Mem: 3007 234 672 30 2100 2523
Swap: 3905 1 3904
coolfire@n01:~$ uname -a
Linux n01 4.4.0-67-generic #88-Ubuntu SMP Wed Mar 8 16:34:45 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
coolfire@n01:~$