Chinese RISC-V project teases 2025 debut of freely licensed advanced chip design
Third-gen Xiangshan may be close to performance of Arm’s made-for-HPC Neoverse 2
A key figure in in China’s drive to develop processors based on the RISC-V instruction set architecture has said the project will deliver in 2025, perhaps with a design that could be a datacenter contender.
The prospect of a 2025 debut appeared on Sunday in a post to Chinese social media service Weibo, penned by Yungang Bao of the Institute of Computing Technology at the Chinese Academy of Sciences.
The academy has created a project called Xiangshan that aims to use the permissively licensed RISC-V ISA to create a high-performance chip, with the Scala source code to the designs openly available.
Bao is a leader of the project, and has described the team's ambition to create a company that does for RISC-V what Red Hat did for Linux – although he said that before Red Hat changed the way it made the source code of RHEL available to the public.
The Xiangshan project has previously aspired to six-monthly releases, though it appears its latest design to be taped out was a second-gen chip named Nanhu that emerged in late 2023. That silicon ran at 2GHz and was built on a 14nm process node.
The project has since worked on a third-gen design, named Kunminghu, and published the image below depicting an overview of its non-trivial micro-architecture.
An overview of the Kunminghu RISC-V micro-architecture ... click to enlarge (Source)
The 64-bit RISC-V Kunminghu blueprint sports multiple parallel processing units capable of integer, floating-point, and vector operations, and what looks like the ingredients for out-of-order execution, thus allowing it to scale from modest to moderately large devices, at least; the project’s most recent progress report mentions simulated testing of a processor that runs at 3GHz.
Bao’s post acknowledges that the project hasn’t progressed as quickly as hoped and argues that’s because developing high-end chips is hard.
The Xiangshan project therefore spent all of 2024 “continuously optimizing the area and power consumption of the third-generation Xiangshan (Kunming Lake architecture), and finally achieved a gap of less than 8 percent compared with N2.”
That’s almost certainly a reference to Arm’s Neoverse 2 CPU core, which the Softbank-owned chip design champ recommends for use in the cloud, HPC, and machine learning applications. We’re pretty sure that Neoverse 2 is the tech Microsoft used for the Cobalt 100 CPU it uses to power Arm servers it rents in the Azure cloud.
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If Xiangshan can deliver a design with similar power it will be enormously significant, for three reasons.
One is that RISC-V is mostly used for modest silicon. Leveling it up, or providing another processor that levels it up, would be a big step forward.
Another is that the project uses the Mulan PSL-2.0 license, which grants a “perpetual, worldwide, royalty-free, non-exclusive, irrevocable copyright license to reproduce, use, modify, or distribute” IP, with modification or not. Xiangshan designs would therefore be free, a contrast to Arm’s license-based business model and the closed proprietary products from Intel and AMD. One only needs to consider how Linux came to dominate the operating system market to understand the potential for Xiangshan to shake up the industry and make trouble for established chipmakers.
A third reason is that the Xiangshan project was started to help China become less dependent on foreign entities. If it delivers processors to rival from those from established players, sanctions that prevent the sale of advanced silicon to the Middle Kingdom may become less potent.
Of course, it may be years before that happens. Despite Bao’s promises, Xiangshan’s third-gen designs are yet to debut or be baked into silicon, from what we can tell; the project has already blown plenty of deadlines; moving from design to working silicon can take ages … and so can the work to encourage developers to target a platform.
Bao’s post is therefore exciting, but the Xiangshan story will play out for many years. ®
Speaking of RISC-V...
Imagination has given up on designing RISC-V CPU cores, and will focus on crafting GPUs for system-on-chips, including those using RV. The biz's private equity owners are also reportedly looking to sell off the operation.