Problem with RAM when installing 16 GB., what is the reason?

Question

AMD

Good evening!
Motherboard - ga-ma790gp-ds4h, phenom II x3 720 Installed
16 GB (kvr800d2n6, 4 by 4) and this is the picture.

If you put a couple of 1 GB sticks in the last 2 slots. everything works great.
What are the options.

Answer 1

For 32-bit processors / OS (I don’t remember), the maximum size of RAM can only be 4 gigabytes, so this error is also possible .