How to find information about the memory you have in your Mac?
The System Profile from the Apple menu will tell you how much and what kind
of memory is in your system.
Open the Apple menu, and choose About This Mac.
Select More Info and the System Profile screen opens, showing the Hardware Overview. This provides you with information you need such as as your Mac model,
and total memory capacity and CPU type and speed.
In the Contents section on the left, click Memory,
this will show your current memory setup. This information will tell you which slots are filled and what type of
memory you have. It will also tell you how many slots are still available.