ARM Cortex-X4: Next-Gen Mobile Computing in the AI Era

Mobile computing evolves rapidly, with ARM’s Cortex-X4 representing a significant advancement in performance. Launched May 2023 as part of ARM’s v9.2 architecture, it builds on previous designs while introducing key improvements for next-gen applications, especially AI-focused ones.

What Makes the Cortex-X4 a Game-Changer?

As ARM’s fourth performance-focused X-series iteration, the X4 maintains its emphasis on peak performance while introducing architectural refinements that deliver gains across multiple metrics.

ARM’s specifications show the X4 delivers 15% better performance than the X3 at identical manufacturing processes and clock speeds, while simultaneously reducing power consumption by 40% for equivalent workloads.

Architectural Innovations Driving Performance

Key enhancements in the X4 include:

• Deeper Pipeline and Enhanced Front-End: Allows higher clock speeds while maintaining throughput, with improved branch prediction and fetch mechanisms.
• Expanded Execution Units: More numerous and capable units with wider decode and dispatch stages for parallel instruction processing.
• Larger Caches: Up to 64KB L1 instruction/data caches and 2MB private L2 cache, reducing memory access latency.
• Advanced Vector Processing: Incorporates SVE2 and Matrix Multiplication acceleration for AI workloads.
• Improved Memory Subsystem: Better prefetching and cache coherency reduce memory access impact.

AI Performance: The New Battleground

The X4’s primary focus is enhanced AI and ML capabilities. As on-device AI becomes essential for photography and real-time translation, ARM has prioritized features accelerating these computations.

Dedicated matrix multiplication acceleration delivers up to 2x performance for certain AI algorithms versus the X3. SVE2 implementation provides flexible vector length support (128-2048 bits) for efficient AI inference.

These improvements support smartphone manufacturers implementing on-device AI features requiring substantial computational power with battery efficiency.

Real-World Performance: Benchmarks and Applications

Early X4 benchmarks show significant improvements: 15-18% better integer performance (general applications) compared to X3 at identical clock speeds.

Floating-point operations show gains up to 20%, while memory-intensive benchmarks demonstrate latency reductions up to 25% for certain access patterns.

These translate to improved user experiences in:

• Gaming: Better frame rates in 3D games, especially in CPU-bound scenarios like physics and AI opponents.
• Camera Processing: Faster computational photography for HDR, portrait mode, and night captures.
• AI Features: More responsive assistants, translations, and content generation.
• Multitasking: Smoother performance with multiple apps and reduced app-switching latency.

Implementation in Commercial Devices

Leading manufacturers have adopted the X4 in flagship SoCs: Qualcomm’s Snapdragon 8 Gen 3, MediaTek’s Dimensity 9300, and Samsung’s Exynos 2400 all use it as their primary high-performance core.

These SoCs typically implement heterogeneous arrangements, pairing X4 cores with efficiency-focused A720 and power-efficient A520 cores. This “DynamIQ” configuration balances performance and power by assigning workloads to appropriate cores.

Samsung’s Exynos 2400 features a single X4 core at 3.2GHz alongside various performance and efficiency cores. Qualcomm’s approach in the Snapdragon 8 Gen 3 uses a single X4 at 3.3GHz with a more balanced core distribution.

Cortex-X4 vs. Competitors

The mobile CPU landscape remains competitive, with Apple’s A-series chips representing the primary performance benchmark.

Compared to Apple’s A17 Pro and A18 cores, the X4 has significantly narrowed the performance gap. While Apple maintains a slight single-threaded edge, the X4 shows competitive multi-threaded performance and strength in AI tasks.

Against other high-performance ARM cores (including Nuvia’s designs), the X4 offers a compelling balance of performance, efficiency, and implementation flexibility for SoC designers.

Power Efficiency: The Critical Balance

While prioritizing performance, the X4 improves energy efficiency with ARM claiming a 40% gain over the X3, addressing a key criticism of previous X-series cores.

This efficiency comes from:

• Enhanced Clock Gating: More granular power control for unused core portions.
• Improved Instruction Retirement: Efficient handling reduces wasted work.
• Better Branch Prediction: Fewer mispredictions minimize wasted execution.
• Advanced Process Nodes: Implementation on 3-4nm processes enhances efficiency.

Future-Proofing: Support for Emerging Workloads

Beyond current performance, the Cortex-X4 addresses future computational needs:

• Enhanced Security Features: Memory tagging and isolation protect against vulnerabilities.
• Advanced SIMD and Matrix Operations: Accelerate AI and machine learning workloads.
• Improved Virtualization: Enables efficient secure environments and containerization.
• Memory Partitioning: Maintains responsiveness during heavy multitasking.

The Bigger Picture: Cortex-X4 in ARM’s CPU Strategy

The X4 is key to ARM’s spectrum of core designs optimized for different targets. This enables SoC designers to create heterogeneous arrangements for specific device categories.

ARM’s three-tier approach—X4 for performance, A720 for balance, A520 for efficiency—offers flexible SoC design options based on market segment and thermal constraints.

Flagship devices typically use one or two X4 cores with several A720 and A520 cores for optimal performance-efficiency balance. Devices with tighter thermal limits may use fewer X4 cores or lower clock speeds.

Developer Considerations and Software Optimization

For developers, the X4 offers opportunities requiring specific optimizations:

• Vectorization: Using SVE2 and NEON instructions for performance gains.
• Memory Access Patterns: Aligning structures to efficiently use the cache hierarchy.
• Heterogeneous Awareness: Understanding workload scheduling across different core types.
• AI Framework Optimization: Leveraging the X4’s matrix multiplication features.

FAQ: Common Questions About the Cortex-X4

Q: How does the Cortex-X4 compare to previous generations?

A: The X4 delivers 15% better performance and 40% better efficiency than the X3, with enhanced AI capabilities.

Q: Which devices use the Cortex-X4?

A: Flagship devices with Snapdragon 8 Gen 3, Dimensity 9300, and Exynos 2400 SoCs.

Q: Does the Cortex-X4 support ray tracing?

A: No dedicated hardware, but improved floating-point performance helps with computational aspects.

Q: How does it impact battery life?

A: Though 40% more efficient, it’s still performance-focused. Devices balance between X4 and efficiency cores.

Q: Can it run desktop applications?

A: Its performance approaches entry-level desktop CPUs, but software compatibility and thermal constraints remain differentiators.

Conclusion: The Significance of Cortex-X4 in Mobile Computing Evolution

The Cortex-X4 represents a major leap in mobile computing, delivering better performance with improved efficiency. Its AI features support next-gen applications using on-device machine learning. In flagship chips, the X4 narrows the mobile-PC performance gap, enabling new productivity, gaming, and content creation possibilities.

Balancing performance, efficiency, and future-ready features, the X4 ensures devices maintain capability throughout their lifecycle, offering strong performance today with capacity for tomorrow’s innovations. Despite Apple’s competitive custom silicon, the X4 showcases ARM’s leadership in developing mobile CPUs within portable device constraints.