2013 is the year that apple started soldering the RAM modules to the board. You want to look in the instructions manual that came with your macbook(the book or the help guide in your computer) to see if the upgrade is possible. If it is then see what the specified mhz is. If you go to apple in the left hand corner->about this mac->The "Memory" tab and look at the number in front of MHz . If not the only way to upgrade or fix memory errors is to buy a new mother board or a different MacBook with the amount of ram you need built in. I am being honest, there are complaints about this solder-in memory everywhere.