Broadcom Delivers Industry’s First 3.5D F2F Technology for AI XPUs

Broadcom announced the availability of its 3.5D eXtreme Dimension System in Package (XDSiP™) platform technology, enabling consumer AI customers to develop next-generation custom accelerators (XPUs). The 3.5D XDSiP integrates more than 6000 mm2 of silicon and up to 12 high bandwidth memory (HBM) stacks in one packaged device to enable high-efficiency, low-power computing for AI at scale. Broadcom has achieved a significant milestone by developing and launching the industry's first Face-to-Face (F2F) 3.5D XPU.

The immense computational power required for training generative AI models relies on massive clusters of 100,000 growing to 1 million XPUs. These XPUs demand increasingly sophisticated integration of compute, memory, and I/O capabilities to achieve the necessary performance while minimizing power consumption and cost. Traditional methods like Moore's Law and process scaling are struggling to keep up with these demands. Therefore, advanced system-in-package (SiP) integration is becoming crucial for next-generation XPUs. Over the past decade, 2.5D integration, which involves integrating multiple chiplets up to 2500 mm² of silicon and HBM modules up to 8 HBMs on an interposer, has proven valuable for XPU development. However, as new and increasingly complex LLMs are introduced, their training necessitates 3D silicon stacking for better size, power, and cost. Consequently, 3.5D integration, which combines 3D silicon stacking with 2.5D packaging, is poised to become the technology of choice for next-generation XPUs in the coming decade.

Broadcom’s 3.5D XDSiP platform achieves significant improvements in interconnect density and power efficiency compared to the Face-to-Back (F2B) approach. This innovative F2F stacking directly connects the top metal layers of the top and bottom dies, which provides a dense and reliable connection with minimal electrical interference and exceptional mechanical strength. Broadcom’s 3.5D platform includes IP and proprietary design flow for efficient correct-by-construction of 3D die stacking for power, clock and signal interconnects.

Key Benefits of Broadcom's 3.5D XDSiP

Broadcom’s lead F2F 3.5D XPU integrates four compute dies, one I/O die, and six HBM modules, leveraging TSMC's cutting-edge process nodes and 2.5D CoWoS^® packaging technologies. Broadcom's proprietary design flow and automation methodology, built upon industry-standard tools, has ensured first-pass success despite the chip’s immense complexity. The 3.5D XDSiP has demonstrated complete functionality and exceptional performance across critical IP blocks, including high-speed SerDes, HBM memory interfaces, and die-to-die interconnects. This accomplishment underscores Broadcom's expertise in designing and testing complex 3.5D integrated circuits.

With more than five 3.5D products in development, a majority of Broadcom’s consumer AI customers have adopted the 3.5D XDSiP platform technology with production shipments starting February 2026. For more information on Broadcom’s 3.5D custom compute platform, please click here.