iFixit has carried out a teardown of the new 21.5-inch iMac with Retina 4K display, and has found that the CPU and RAM-two of the components you are most likely to upgrade at some point-are both modular.
However, accessing and replacing these two basic components isn't exactly easy. Armed with the right tools and guide, someone could could at least double the base 8 GB of memory, turning their new iMac with Retina Display into an iMac Semi-Pro, according to iFixit.
This is the first time Apple has had a 21.5-inch iMac with expandable RAM since 2013, and the first modular CPU since 2012.
iFixit notes that Apple may have reverted to a socketed CPU because that's all Intel has at the moment - there are no desktop-class Kaby Lake CPUs in a BGA package.
In any case, the iMac remains not easy to open. Everything is buried under a finicky glass panel. It requires a speciality pizza-cutter-like tool to breach the adhesive before any repair.