Rain AI

Rain AI is a company developing a new AI compute platform by co-designing every layer of the AI stack. Rain AI aims to lower the abstraction between neural networks and their implementation in silicon. The company claims its co-design offers new levels of performance for AI compute. Its chip design, called a neuromorphic processing unit (NPU), replicates features of the human brain. Rain has stated its technology is analog, not digital. It uses a circuit called a memristor on top of silicon wafers that serve as "artificial synapses," allowing for the processing and memory to happen in the same place, potentially improving the speed and energy efficiency of AI models compared to more traditional digital AI chips.

Rain AI licenses its intellectual property (IP) for custom System on Chips (SoCs) with plans to release AI chip hardware. IP licensing includes Rain's digital in-memory compute tile and software stack tailored for on-device AI workloads.

Rain AI's co-design approach includes the following:

• Digital In-Memory Compute (D-IMC)—Rain AI's proprietary D-IMC cores scale to high-volume production, training, and inference, and refine AI processing, data movement, and data storage. Combined with the company's quantization algorithms, their AI accelerators maintain FP32 accuracy.
• Numerics—Rain AI’s block brain floating point scheme prevents accuracy loss compared to FP32. The numerical formats are co-designed at the circuit level with the D-IMC core, leveraging performance gains of optimized 4-bit and 8-bit matrix multiplication.
• RISC-V—Rain AI utilizes the open standard instruction set architecture RISC-V ISA, allowing AI developers greater flexibility to implement operators and compile models. The company has developed a proprietary interconnect between RISC-V and D-IMC cores.
• On-device fine-tuning—Rain AI is co-designing fine-tuning algorithms with hardware to facilitate efficient real-time training.

Originally called Rain Neuromorphics, the company was founded in 2017 by Jack Kendall (CTO), Gordon Wilson (executive advisor), and Juan Claudio Nino (board member). Wilson was CEO of the company for six years from its founding until William Passo (formerly Rain's COO) took the role in 2023. The company was incubated at Y Combinator. Rain's VC partners include Y Combinator, Daniel Gross, Jaan Tallinn, Founders X Fund, Airbus Ventures, Liquid 2 Ventures and Deepwater. One of the company's seed rounds was led by Sam Altman. In February 2022, the company announced it had raised $25 million in series A funding led by Prosperity7. The series A round brought the company's total funding to $33 million. According to disclosures to investors, the funding is enough to operate through to early 2025 and valued the company at $90 million.

On November 30, 2023, the US government forced Prosperity7, a Saudi Aramco-backed venture capital firm, to sell its shares in Rain AI. Prosperity7 was a lead investor in the 2022 $25 million round for Rain AI. The decision came after a review by the Committee on Foreign Investment in the United States. Documents revealed in December 2023 showed that OpenAI had signed a letter of intent four years previously to spend $51 million on chips developed by Rain. OpenAI CEO Altman is a personal investor in the company, investing over $1 million in the company. The letter is a nonbinding agreement to spend $51 million on chips when they become available. Investor documents show that Rain is planning to release its first hardware to customers in October 2024.