The answer to whether Arm is really faster than x86 is not straightforward. Both processor architectures have their strengths and weaknesses. However, in recent years Arm has made significant advancements in performance that rival x86 in many workloads. The key factors to consider are:
Arm processors are designed to be power efficient for use in mobile devices. Using less power enables longer battery life. The Arm architecture uses a reduced instruction set computer (RISC) design that requires fewer transistors. This makes Arm chips smaller, cooler running, and more energy efficient than x86 Complex Instruction Set Computer (CISC) chips. The focus on power efficiency gives Arm an advantage in performance per watt.
x86 processors traditionally had much higher clock speeds than Arm. A 4 GHz x86 CPU was common whereas Arm mobile chips ran below 2 GHz. However, thermal constraints limited how fast x86 chips could run before overheating. In recent years, Arm has closed the clock speed gap with high-end Arm server CPUs now boosting beyond 3.3 GHz. While x86 still has a clock speed advantage, Arm has reduced the disparity.
Instructions Per Cycle
Along with clock speed, a key determinant of processor performance is how many instructions can be executed per cycle (IPC). Complex x86 CISC chips can execute more instructions per cycle which compensates for lower clock speeds. RISC Arm chips execute fewer instructions per cycle. However, thanks to architectural improvements, latest high-end Arm processors like the Cortex-A78 can achieve up to 4 IPC nearing x86 levels.
Branch prediction is a technique used to minimize pipeline stalls by speculatively executing instructions ahead of branches before the direction is known. Arm originally lagged behind x86 in branch prediction capabilities. But new Arm designs greatly improved predictive abilities to be comparable to x86. Neoverse N2 cores have a Branch Target Address Cache to accelerate branch speculation.
Out-of-order execution is used to prevent pipeline stalls by executing instructions in parallel or re-arranging order when data dependencies allow it. ARM historically performed in-order execution which sequentially processes instructions. But starting with Cortex-A15, ARM added out-of-order capabilities. The Neoverse N2 even has a 512-entry reorder buffer exceeding many x86 designs.
Larger cache improves performance by reducing latency of fetching data from main memory. x86 processors traditionally had larger L1, L2, and L3 cache sizes compared to Arm chips for mobile. For example, latest high-end x86 chips may have 24MB L3 cache versus 4MB for mobile Arm. However, Arm’s cache has been steadily improving. The Neoverse N2 has 64KB L1, 1MB L2, and up to 64MB L3 system-level cache comparable to x86 servers.
Vector processing allows a single instruction to execute mathematical operations across multiple data elements in parallel. Intel AVX and ARM Neon are respective vector extensions. Neon was less powerful than AVX giving x86 an advantage in HPC and AI workloads. But new ARMv9 architecture adds SVE2 to significantly improve vector performance rivaling AVX-512 in computations per cycle.
Multithreading enables a processor to switch between threads to keep more cores utilized. Both x86 and Arm support simultaneous multithreading to execute instructions from different threads in parallel. However, Arm typically has offered fewer threads per core such as 2-way SMT versus 4-way on high-end Xeons. The latest Neoverse N2 matches x86 with 4-way SMT.
Higher core counts allow more operations to run in parallel. X86 chips historically packed more cores on a single die because Arm was focused on power-constrained mobile SoCs. For example, Intel Xeons may have up to 40 cores while Arm mobile chips had 4-8. However, new server-focused Neoverse designs match x86 with up to 128 cores planned for next-gen.
The manufacturing process node determines transistor density. Intel was long ahead in x86 fabrication technology enabling greater performance at lower power. But Arm chip designers like TSMC and Samsung have caught up or surpassed Intel reaching 5nm while x86 remains stuck at 10nm. The level playing field in manufacturing allows Arm performance to keep pace.
Performance per Dollar
ARM chips excel in delivering better performance per dollar. ARM-based processors are cheaper as intellectual property that can be licensed and manufactured by many semiconductor fabs. The competitive market for Arm chips results in lower pricing. In contrast, x86 CPUs are only made by Intel and AMD. Arm’s cost advantage allows more cores and features at a lower price point.
Performance per Watt
The ultimate benchmark is performance achieved within a fixed power envelope. ARM’s historical advantage has been delivering higher compute efficiency than power-hungry x86. The flexible RISC architecture and competitive manufacturing means Arm excels in embedding powerful yet efficient processors into everything from mobile to servers. So performance-wise Arm has caught up to x86 while maintaining a superior performance per watt.
Customization and Integration
ARM’s licensable business model allows processor designs to be customized for a target application. SoC integrators can add or remove features to optimize Arm cores for their workloads. Tight integration with on-chip accelerators saves power and boosts performance. In contrast, x86 CPUs are general purpose making them less customizable for specialized tasks.
The ARM ecosystem was historically targeted at low-power mobile applications rather than servers and PCs. Software support and optimization for the architecture has lagged behind x86. However, as ARM penetrates the data center the ecosystem is maturing quickly. Microsoft now supports ARM chips enabling edge computing scenarios. The open RISC architecture also benefits Linux adoption.
In summary, ARM and x86 each have unique advantages that make them suitable for different applications. However, thanks to architectural improvements, fabrication advancements, and ecosystem maturity, ARM has achieved performance and compute efficiency rivaling top-tier x86 processors across a wide range of workloads. So while blanket claims that “ARM is faster” may be oversimplified, the innovation of the past decade in ARM performance merits serious consideration alongside x86 in modern computing.