Recently, at the Arm UNLOCKED summit, Arm officially launched the Arm Lumex Compute Subsystem (CSS) for mobile devices, which includes the new C1 series CPU cluster based on the Armv9.3 instruction set, as well as the Mali G1 GPU series that supports the next generation of ray tracing technology. In a media interview following the event, Arm executives indirectly addressed the controversy surrounding Xiaomi’s launch of the Arm architecture self-developed chip, the Xuanjie O1, this year.
On May 22nd, Xiaomi’s first 3nm flagship SoC, the Xuanjie O1, was officially released, and Arm’s official website published a press release titled “XRING O1 Custom Silicon from Xiaomi is Powered by the Arm Compute Platform.” Many netizens interpreted this literally, believing that the Xiaomi Xuanjie O1 is a custom chip designed by Arm based on its CSS for Client. Although at that time, Chip Intelligence interviewed Xiaomi’s chip head, Zhu Dan, who refuted this claim, Arm also deleted that press release and reissued a corrected version, but it still did not quell various external doubts.
In the media interview after the Arm UNLOCKED summit, Chris Bergey, Arm’s Senior Vice President and General Manager of the Client Line of Business, pointed out that leading smartphone manufacturers like Xiaomi developing their own chips is a significant trend, as companies like Apple, Samsung, and Huawei have been moving in this direction to varying degrees for many years. This is actually a trend faced by the entire technology industry. Not only smartphone manufacturers want to develop their own chips, but data center and automotive manufacturers (especially in the massive automotive market in China) are also seeking customized chips.
Against this backdrop, the Arm CSS platform was born to respond to this trend. Therefore, Arm was the first to launch the Arm Neoverse CSS for servers in 2023, the Arm CSS for Client in 2024, the Zena CSS for automotive in June 2025, and the newly launched Arm Lumex CSS.
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However, the core capabilities of these companies lie in operating data centers, manufacturing cars or smartphones, rather than designing CPUs. For self-developed chips, while integrating Arm’s CPU and GPU is certainly important, it is not the core expertise of these companies.
Chris Bergey emphasized that this is precisely why the Arm CSS platform is significantly valuable to them: “They no longer need to hire hundreds of engineers to integrate our IP; instead, they can focus on the parts that truly bring differentiation—such as autonomous driving accelerators, ISP and imaging processing pipelines on mobile devices, or specific workload accelerators deeply coupled with computing units in data centers.”
In simple terms, the Arm CSS platform can provide customers with a more complete CPU/GPU cluster solution and software stack, as well as a physical layout based on advanced process nodes, which will help customers significantly reduce their investment in the R&D of CPU/GPU clusters for self-developed chips, allowing them to focus more on their core differentiated R&D needs, improving the success rate of chip tape-outs and accelerating product launch cycles.
Chris Bergey explained: “They no longer need to hire hundreds of engineers to integrate our IP; instead, they can focus on the parts that truly bring differentiation—such as autonomous driving accelerators, ISP and imaging processing pipelines on mobile devices, or specific workload accelerators deeply coupled with computing units in data centers. This is the core advantage of Arm and our CSS platform. We provide a validated computing foundation that allows customers to achieve the customization they need at a relatively low cost. The real value is not in creating an Arm CPU that is better than what Arm engineers design—in fact, even if they could, the performance improvement would be at most around 5%; the real value increment lies in the fact that by building their own SoC on the Arm platform, they can create an additional 50%, 100%, or even 200% of value.”
Although Arm did not directly respond to previous external doubts about whether “the Xiaomi Xuanjie O1 is an Arm custom chip” or “the Xiaomi Xuanjie O1 is based on Arm CSS customization,” James McNiven, Vice President of Product Management for Arm’s Client Line of Business, also clearly pointed out during the interview that currently, Arm’s CSS platform only focuses on its strengths in CPU, GPU IP, and cluster solutions, providing customers with reference designs and physical implementations, which does not mean that Arm utilizes the Lumex CSS platform to customize complete SoC solutions for customers. Customers also cannot use the Lumex CSS platform to directly hand over to foundries to produce their own chips, as SoCs cannot run with just CPUs/GPUs; this does not constitute a complete SoC solution. Customers still need to add a series of their own IP or third-party IP to create a complete SoC solution based on the Lumex CSS platform, such as interface IP, ISP, NPU, baseband IP, etc.
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Note: The cover image of this article is from freepik, self-made by the author, and publicly available media materials, all authorized.
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