Only the 27-inch model allows swapping the RAM modules, and that’s about it
For one reason or another, the talented designers at 1 Infinite Loop, Cupertino, California decided that the 21.5-inch version of the iMac would not offer any upgrading options. Not even in the RAM department, where previous-generation models would allow users to swap the memory modules themselves.For all the oomph it presents, Apple’s new iMac – more precisely, the base-configuration – will not allow you to upgrade its memory. In other words, Apple's all-in-one desktop solution is completely non-upgradable at this point.
With previous-generation models, users could easily unscrew a tiny metal plate located in between the speakers at the bottom of the computer and swap the SO-DIMMs themselves, should they require an upgrade from say, 2 gigs of memory to 4GB.
That’s not the case anymore with the 2012 version of the entry-level 21.5-inch iMac, according to Apple’s marketing pages describing the computer’s key features. The option to upgrade the RAM is only available with the high-end 27-inch model now.
“The 21.5-inch iMac comes with 8GB of memory and can be configured online with 16GB. On the 27-inch iMac, 8GB of memory comes standard, and you can upgrade to 16GB or 32GB,” says Apple.
“Configure and buy your iMac at the Apple Online Store and it will arrive with the memory already installed. Or add more memory to the 27-inch model yourself by popping open the easy-to-access memory panel on the back,” reads the company’s marketing pitch.
In other words, professionals looking to employ the new iMac as a workstation for their day-to-day tasks should seriously consider a build-to-order option with 16GB of memory out-of-the-box.
Alternately, the 27-inch version sounds like the better option, considering the added benefit of RAM upgradability and, of course, the increased screen real estate.