Zen 2 is a significant departure from the physical design paradigm of AMD's previous Zen architectures, Zen and Zen+. Zen 2 moves to a multi-chip module design where the I/O components of the CPU are laid out on its own, separate die, which is also called a chiplet in this context. This separation has benefits in scalability and manufacturability. As physical interfaces don't scale very well with shrinks in process technology, their separation into a different die allows these components to be manufactured using a larger, more mature process node than the CPU dies. The CPU dies (referred to by AMD as or CCDs), now more compact due to the move of I/O components onto another die, can be manufactured using a smaller process with fewer manufacturing defects than a larger die would exhibit (since the chances of a die having a defect increases with device (die) size) while also allowing for more dies per wafer. In addition, the central I/O die can service multiple chiplets, making it easier to construct processors with a large number of cores.
