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Arm’s September 2025 Lumex launch introduced four C1 CPU cores for flagship smartphones and positioned the broader platform for next-generation PCs. Lumex is more than a processor: it combines C1 CPUs, built-in SME2 matrix instructions, GPUs and system IP. Arm’s launch did not identify a shipping C1-based PC, so the PC connection is a platform target rather than a confirmed laptop product.
What Arm announced: Lumex and the C1 CPU family
On September 10, 2025, Arm announced Lumex, a configurable compute subsystem built around an Armv9.3 C1 CPU cluster and Scalable Matrix Extension 2 (SME2), alongside GPU and system IP. Arm describes it as a platform for flagship smartphones and next-generation PCs. Device makers can use its physical implementation or configure the platform RTL for their target tier and harden the cores themselves. Arm says its optimized physical implementations target 3nm nodes; that does not mean every Lumex-based chip uses a particular foundry’s 3nm process. Arm’s announcement and its engineering blog describe the platform and implementation options.
How the four C1 cores differ
The C1 names identify cores with different performance, area and power roles, not four interchangeable versions of one design. The figures below are Arm-reported launch comparisons, not independent retail-phone benchmarks.
| Core | Intended role | Arm-reported comparison |
|---|---|---|
| C1-Ultra | Peak performance for flagship devices | 25% higher single-thread performance than Cortex-X925. |
| C1-Premium | Sub-flagship performance in a smaller area | Up to 35% smaller area than C1-Ultra, with comparable sustained performance. |
| C1-Pro | Sustained performance for workloads such as gaming and streaming inference | 16% higher sustained performance in Arm’s launch table. |
| C1-Nano | Low-power operation for always-on AI and compact devices such as wearables | 26% efficiency improvement in Arm’s launch material, using less area. |
Arm’s current CPU catalog also describes C1-Ultra as delivering 25% higher single-thread performance than Cortex-X925, C1-Premium as up to 35% smaller than C1-Ultra, C1-Pro as 16% faster in gaming, and C1-Ultra as providing a 15% average speed increase in real-world applications. These are Arm product claims; they are not a single, directly comparable test across all four cores.
#1 Best Overall
What SME2 adds for on-device AI
SME2 is integrated into the C1 CPU architecture to accelerate matrix-heavy tasks. Arm identifies speech recognition, image and video processing, computer vision, large language model inference and assistant functions as relevant workloads. Software support—including Arm KleidiAI and supported frameworks—is part of the platform’s effort to make these capabilities usable by applications.
Arm’s launch materials report up to 5× AI performance for an SME2-enabled C1 cluster versus the previous-generation CPU cluster, 4.7× lower latency for speech workloads and 2.8× faster audio generation. These are Arm’s comparisons from 2025, not independent measurements of a phone in general use. The figures refer to different workloads and should not be treated as one combined result.
Rank #2
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In a technical blog, Arm reported an average 30% performance uplift across six benchmarks versus the previous-generation CPU cluster under the same conditions. The same blog reported an average 15% speed-up across selected applications such as gaming and video streaming, and average 12% less power across selected daily mobile workloads including video playback, social media and web browsing. Those averages apply to Arm’s selected comparisons, not every application or device. Arm’s technical explanation provides that test framing.
Arm also demonstrated neural camera denoising at more than 120 frames per second at 1080p or 30 frames per second at 4K on a single core. That is a demonstration claim, not a guarantee of camera performance in all C1 phones.
Rank #3
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- FAST. POWERFUL. AI-READY: Power through your day with AI-accelerated performance from our fastest, smoothest and most powerful Galaxy processor yet, built to keep up with everything you do
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Does this mean an AI PC with C1 is available?
No specific shipping C1-based PC was identified in Arm’s September 2025 launch materials. Arm said Lumex was purpose-built for flagship smartphones and next-generation PCs, and its engineering blog discussed mobile and PC devices. This establishes the platform’s intended scope, not the availability of a named laptop using C1. A PC maker would need to confirm a product and its hardware details before C1 could be described as powering a shipping AI PC.
The practical AI-PC connection is that the same configurable platform approach and SME2-capable CPU architecture can serve more than smartphones. It does not establish that every Lumex implementation includes the same GPU, system configuration, performance characteristics or software support.
Rank #4
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- FAST. POWERFUL. AI-READY: Power through your day with AI-accelerated performance from our fastest, smoothest and most powerful Galaxy processor yet, built to keep up with everything you do
- RICHER COLOR. SHARPER DETAIL: The ultra-vivid display on Galaxy S26+ automatically makes every image sharper for a more immersive experience
- FIT EVERYONE IN THE SHOT: Group selfies are easier on your Samsung phone with a wider front camera⁴ that captures more of the scene, so no one gets left out of the moment
Where C1 has appeared in phones
Arm reported in November 2025 that the vivo X300 series uses Lumex C1 CPUs and Mali G1-Ultra graphics. Arm also cited its own device-performance claims for that series: 20% faster live translation and 30% quicker image recognition. Those are vendor-reported outcomes, not independent review results. Arm additionally named OPPO among early device makers using Lumex technologies. Arm’s vivo report is the source for these ecosystem details.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsWhat changed after the C1 announcement
On September 8, 2026, Arm announced CSS for Mobile 2, a newer mobile platform with a C2 CPU cluster that includes C2-Ultra and C2-Pro. This is subsequent mobile-platform context; it is not part of the 2025 C1 launch, and the announcement alone does not establish availability in shipping devices. Arm’s C2 announcement describes the newer platform.
Quick Recap
How to interpret Arm’s performance figures
- Check the baseline. A percentage against Cortex-X925, a previous-generation CPU cluster or a selected application answers a different question.
- Separate peak from sustained performance. A peak single-thread figure does not predict prolonged gaming or streaming workloads, where thermal limits and device design matter.
- Distinguish core claims from phone results. The final system depends on the maker’s chip configuration, GPU and other integration choices.
- Look for independent device testing before ranking it against competitors. The launch figures do not establish a cross-vendor ranking; that requires comparable devices, test methods, power and thermal conditions, and sustained results.
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