Upgrading your iMac with more RAM is super-easy and requires only a few steps. In these cases, sadly you will need to pay higher prices to get the upgrade you want. Memory isn't removable by users on every 21.5-inch iMac since the late 2012 model despite it being possible to do on 27-inch models. There are a few situations, though, where you might need to contact Apple or an Apple authorized service provider to install the RAM. IMac RAM upgrades are easy for most models, and it’s a good idea to do it yourself, for two reasons: firstly you’ll get to know your iMac better, and secondly it’s possible to save a few hundred bucks rather than having Apple do the expensive upgrade.

Also, with physical memory available, macOS won’t need to resort to using virtual memory, which ultimately slows things down. Just consider the fact that the more RAM your iMac has installed, the more windows and/or tabs it can have open at one time without slowing down. Why? The answer is very easy: there is no such thing as too much system memory. You might have heard plenty of times that it’s better to buy a Mac with the maximum amount of RAM (random access memory).

For apple instal Barbie 2017 Memory