ram compatibility T440s

[davidgurvich]

I attempted 4 different sticks of 4GB DDR3 ram and system booted fine with no errors but ram wasn't detected. Don't recall the brands but good quality. I thought the T440s only took DDR3L but then saw a spec sheet from lenovo that made me think otherwise.
Installed 1 stick 8GB DDR3L and got the 1331 beep code. Samsung ram.
Installed 2nd stick 8GB DDR3L and booted fine with 12GB detected. Mushkin ram

All the ram works in other systems, including the 2 8GB sticks together. At first I thought ram slot was broken because no beep codes from the 4GB DDR3 ram. Then the Samsung ram caused a beep code and I was confused. Then Mushkin ran with no issues and I was more confused, especially since I pulled the 8GB sticks from a system where they were installed together.