How to see the actual memory and its properties (slot position, size, speed...)
lshw -short -C memory
or
dmidecode
I find the following more more Human friendly and it gives the Speed, Size, Slot, Dimm Type, etc...
sudo dmidecode -t memory
If you only need to know the actual maximum memory and amount of slots in your motherboard then do the following:
sudo dmidecode -t 16
Changing 16 for 17 will give you an more detail look at each memory slot in your motherboard.
sudo lshw -class memory worked for me.
Under
*-memory
You should see
*-bank:0
and
*-bank:1
If you have 2 slots. Only *-bank for 1 slot.