The demise of Moore’s Law has been much debated among engineers and experts at this point. Also, as silicon-based transistors got smaller and smaller, manufacturers had to contend with increased temperature density (more transistors in a smaller area generates more heat).
And even though chiplet technologies such as TSMC’s InFO_LI and Intel’s Foveros 3D technology have improved their capabilities and allowed multiple chips to be paired within the same board, connecting these chips together is , requires a wire carrying electrons. Flying electrons mean higher temperatures (by passing through the resistance of the semiconductor) and increased power consumption.as covered in register, the startup Lightmatter has another idea. The idea is to connect chips without using any electrical wiring at all. The company has embraced HotChips in photonics as an alternative.
“Arrays of electrically interconnected chiplets are fundamentally plagued with problems such as power consumption concatenation,” said Nicholas Harris, Lightmatter founder and CEO, at the company’s HotChips presentation. says.
The issue is clear and well-recognised. The more chiplets connected to a single package, the more interconnections are required as the chiplets must connect to each other to exchange the data needed for computation. Electricity is a fast medium, but it is not the fastest medium available. That prize is reserved for light. The company’s passage technology Thus, we aim to usher photonics into the chiplet era by allowing different chips to be interconnected via nanophotonic waveguides. They basically use photons (instead of the more ubiquitous electrons) to carry information, with very little signal loss and much increased bandwidth.
Interestingly, AMD itself has also explored photonics designs that enable information transfer in its architecture. For that part Intel has a dedicated research center.
“The passage is diced from a 300mm silicon photonics wafer, with lasers, optical modulators, photodetectors, and transistors all integrated into the platform,” Harris continues.
The interconnected chiplets (ASICs, CPUs, GPUs, memory chips, etc.) sit on top of this photonics-enabled ‘sandwich’.
“Because the passage integrates a laser and a transistor, the copackaged chip does not have to deal with the complexity of the photonics elements of transmitting, receiving, or circuit switching,” Harris said. “Each aisle tile can house an array of heterogeneous chips. For example, one tile might contain two different types of his ASICs and two he HBM stacks.”
The company claims that its approach results in less than 2 nanosecond hop times between information exits and entrances, regardless of the distance between the points (so the farthest chiplet is the same as the nearest chiplet). speed). The nanophotonic waveguides used by Lightmatter have the advantage of being much smaller than traditional fiber optic interconnects. The company says it can fit up to 40 waveguides in the space of a single fiber.
According to Lightmatter, this will allow each die to deliver 96 TBps of bandwidth.in comparison with AMD’s Infinity Fabric has a theoretical maximum bandwidth of 800 GbpsOff-chip communication from Passage to other systems over fiber arrays peaks at around 16 TBps.
Additionally, Passage is a fully customizable interconnect on package, eliminating the need for manufacturers to design their own interconnect designs (such as AMD’s Infinity Fabric or Intel’s EMIB). Simply drop the device into a photonics-driven pathway that can accommodate up to 48 full reticle chips (full reticle means these chips can occupy as much area as the manufacturing process allows) and they .
Despite this being entirely photonic, the chips implanted in the Passage are more traditional silicon-based transistor types, meaning they require electrical communication. This is also supported by using through silicon vias (TSVs) to power the die and support PCIe and CXL standards.
Moore’s Law is not dead, but thanks to the ingenuity of chip designers. Lightmatter’s approach is just one of his in a series of steps aimed at keeping computing accelerated today and tomorrow. The only question is how willing a major chip company will be to adopt Lightmatter’s technology when they’re spending so much money and engineering resources on their own.
