The chip industry is exploring new methods for connecting chiplets as the sector moves towards multi-chiplet designs. Researchers at CEA-Leti, a European technology research institute, have proposed using silicon photonics-based optical interposers as a solution for chipset interconnects. This approach, using active optical interposers called Starac, could boost the adoption of multi-chiplet designs, which are increasingly seen as a power-efficient strategy in the CPU and GPU markets.
Chiplets combine multiple chips into a single package to improve processing power without solely relying on shrinking the process node. While offering design flexibility, effective interconnect methods are critical. CEA-Leti’s research suggests optical interposers, based on silicon photonics, could be a significant improvement, reducing communication delays between chiplets.
Starac interposers integrate both electronic and photonic circuitry, enabling complex data routing and processing within a single package. A key feature is the dedicated Optical Network-on-Chip (ONoC) for high-speed data transmission between chiplets, bypassing slower, traditional methods. CEA-Leti claims Starac has the potential to significantly reduce latency, increase bandwidth, and improve power efficiency, making it attractive for mainstream chip manufacturers.
While Starac is still in development, CEA-Leti is seeking industry collaborations to overcome manufacturing complexities and high costs associated with the technology. Jean Charbonnier, R&D project leader at CEA-Leti, explained that in large computing systems, accessing distant high-bandwidth memories (HBMs) across multiple chiplets can introduce latency. He believes Starac’s optical network can drastically cut latency compared to conventional architectures. The institute aims to form industrial partnerships within the next year to address process and packaging challenges and explore real-world applications for this technology.
This innovation highlights the industry’s exploration beyond traditional scaling methods like Moore’s Law. Companies like NVIDIA have previously demonstrated alternative approaches to enhance computing performance, and optical interposers represent another potential path forward for chip technology.
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