Will wonders ever cease? First Apple embraces NFC, now the new iMacs have upgradeable processor and RAM. Okay, the 27" iMacs from 2015 made it easy to upgrade RAM, but the 21.5" version was locked down. That changes with the new 21.5" models, even if it's not an easy process. This is the first time we see an iMac CPU that isn't soldered since 2012! Here's the deal. All-in-Ones like the iMac were not made to be easily serviceable, so you'll have to be careful as you pry open the display (it's secured with adhesive tape). Things get a little tricky as you remove the right speaker, but it's...
Source: http://www.gsmarena.com/the_new_215_imacs_have_upgradeable_processors_and_ram-news-25491.php