Actually he is correct. The 2012 15" retina has the RAM soldered to the board. The 2012 15" without the retina display does have removable RAM chips. So yes upgrading the 2012 Retina does take some pretty good soldering skills. Here is an image of the 2012 15" Retina motherboard

https://d3nevzfk7ii3be.cloudfront.net/ig...