AMD Unveils ‘Chiplet’ Design Approach: 7nm Zen 2 Cores Meet 14 nm I/O Die
AMD on Tuesday disclosed some additional details about its upcoming codenamed Rome processor based on its Zen 2 microarchitecture. As it turns out, the company will use a new design approach with its next-generation EPYC CPUs that will involve CPU ‘chiplets’ made using TSMC’s 7 nm manufacturing technology as well as an I/O die made using a 14 nm fabrication process.
AMD’s chiplet design approach is an evolution of the company’s modular design it introduced with the original EPYC processors featuring its Zen microarchitecture. While the currently available processors use up to four Zen CPU modules, the upcoming EPYC chips will include multiple Zen 2 CPU modules (which AMD now calls ‘chiplets’) as well as an I/O die made using a mature 14 nm process technology. The I/O die will feature Infinity Fabrics to connect chiplets as well as eight DDR DRAM interfaces. Since the memory controller will now be located inside the I/O die, all CPU chiplets will have a more equal memory access latency than today’s CPU modules. Meanwhile, AMD does not list PCIe inside the I/O die, so each CPU chiplet will have its own PCIe lanes.
Separating CPU chiplets from the I/O die has its advantages because it enables AMD to make the CPU chiplets smaller as physical interfaces (such as DRAM and Infinity Fabric) do not scale that well with shrinks of process technology. Therefore, instead of making CPU chiplets bigger and more expensive to manufacture, AMD decided to incorporate DRAM and some other I/O into a separate chip. Besides lower costs, the added benefit that AMD is going to enjoy with its 7 nm chiplets is ability to easier bin new chips for needed clocks and power, which is something that is hard to estimate in case of servers.
This is a breaking news. We are updating the news story with more details.