Intel’s Interconnected Future: Combining Chiplets, EMIB, and Foveros

While Intel works on getting its main manufacturing process technology on track, it is spending just as much time and effort in researching and developing the rest of the chip ecosystem and how it is all connected. On a call with Intel’s process and product team, the company confirmed a few details about how Intel is pushing the boundaries of new technologies with its upcoming high profile graphics products.

An Insight into Intel’s Strategy on Chiplets and Packaging
In a call with Intel last week, we spoke with Ramune Nagisetty, the Director of Intel’s Process and Product Integration, to discuss Intel’s strategy with regard to chiplets and packaging technologies. Ramune has spent over twenty years at Intel, working in areas such as transistor definition for 65nm, Intel Labs for technical strategy and wearables, and most recently as heading up Intel’s chiplet strategy for product integration. Ramune focuses on the art of the chiplet or the packaging in its own right, rather than the specific technologies it goes into, and it was an enlighting discussion.The story around chiplets is going to be a cornerstone of the semiconductor market for the next generation, being able to provide smaller silicon for specific tasks and connecting them together. Chiplets form the basis of Intel’s current Stratix 10 FPGA product line, and the future of Intel Agilex, as well as consumer products like Kaby Lake G with its HBM chiplet for fast high-speed memory. How Intel integrates its own chiplets, with the company confirming it is working on migrating its AI portfolio into chiplet form factors, as well as other third party IP, is going to be an important strategy going forward. The art of connecting chiplets, however, is all in the packaging. Intel has several technologies of its own that it uses.

EMIB, Foveros, Interposers: Connect the Data
Intel’s Embedded Die Interconnect Bridge ‘EMIB’ has been a talking point for a couple of years now. Because certain high-performance chiplet designs require high-bandwidth links with many more traces than traditional organic chip packaging can support, there is a need for more exotic means to build these dense connections. The ‘brute force’ solution here is a silicon interposer, essentially stacking chips on top of a large, ‘dumb’ silicon die that’s in place solely for routing purposes.

With EMIB however, rather than using a full silicon interposer, Intel equips a substrate with just a small embedded silicon connection, allowing a host chip and a secondary chiplet to connect together with high bandwidth and small distances. This technology is currently in Intel’s FPGAs, connecting the FPGA to memory or transceivers or third-party IP, or in Kaby Lake-G, connecting the Radeon GPU to on-package high bandwidth memory.

Intel has also uses full interposers in its FPGA products, using it as an easier and quicker way to connect its large FPGA dies to high bandwidth memory. Intel has stated that while large interposers are a catch-all situation, the company believes that EMIB designs are a lot cheaper than large interposers, and provide better signal integrity to allow for higher bandwidth. In discussions with Intel, it was stated that large interposers likely work best for powerful chips that could take advantage of active networking, however HBM is overkill on an interposer, and best used via EMIB.

Akin to an interposer-like technology, Foveros is a silicon stacking technique that allows different chips to be connected by TSVs (through silicon vias, a via being a vertical chip-to-chip connection), such that Intel can manufacture the IO, the cores, and the onboard LLC/DRAM as separate dies and connect them together. In this instance, Intel considers the IO die, the die at the bottom of the stack, as a sort of ‘active interposer’, that can deal with routing data between the dies on top. Ultimately the big challenges with a multi-die strategy come with in thermal constraints of the dies used (so far, Intel has demonstrated a 1+4 core solution in a 12x12mm package, called Lakefield), as well as aligning known good die for TSV connections.

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