Arm and x86 are the two most common CPU architectures used in personal computers and mobile devices today. Both have their strengths and weaknesses when it comes to performance, power efficiency, cost, software support and more. This article provides an in-depth comparison between Arm and x86 to help you understand the key differences.
Overview
Arm CPUs are based on the ARM architecture developed by Arm Holdings, while x86 CPUs are based on the x86 architecture originally created by Intel. The key difference lies in their underlying design philosophy:
- Arm is a reduced instruction set (RISC) architecture that uses simpler, low-power instructions
- x86 is a complex instruction set (CISC) architecture optimized for performance
This leads to differences in their typical use cases:
- Arm CPUs excel in mobile devices where power efficiency is critical
- x86 CPUs are favored in PCs and servers where peak performance is most important
But the lines are blurring as Arm chips gain performance and x86 chips become more power efficient. Both architectures now span everything from tiny microcontrollers to server processors.
Performance
In the past, x86 CPUs were clearly faster than Arm chips. But Arm has rapidly closed the performance gap in recent years as Moore’s law has slowed down and power constraints have become more important.
Top-end Arm CPUs like the Apple M1 can now compete with x86 chips in single-threaded performance. But x86 still has an edge in multi-threaded workloads thanks to its greater core counts and architectural advantages.
x86 also supports wider SIMD vectors and mature hyperthreading technology for better parallelism. Arm’s SVE and earlier NEON SIMD implementations are catching up but not quite on par yet.
So for lightly threaded general usage, Arm can match x86. But for intensive workloads like gaming, video editing and scientific computing, x86 retains a clear performance lead.
Power Efficiency
Power efficiency has always been a key focus for Arm. The underlying RISC architecture uses simpler instructions that compile to fewer micro-operations, resulting in lower power draw per instruction.
Arm CPUs also benefit from advanced manufacturing processes – major Arm licensees like Apple, Qualcomm and Samsung fabricate chips on leading edge nodes. The ARM ISA is designed from the ground up for mobile power constraints.
In contrast, x86 is a CISC architecture with complex instructions not optimized for power efficiency. x86 CPUs must also maintain backwards compatibility with older x86 software, limiting opportunities for innovation.
As a result, Arm CPUs achieve significantly better performance per watt than x86 chips. For example, the Apple M1 offers laptop-class performance with passive cooling, something unheard of in x86 designs.
Cost
Arm-based processors are generally cheaper than x86 processors with equivalent performance. This is due to several factors:
- Arm has lower licensing costs compared to x86
- Arm instruction set enables leaner, lower transistor count designs
- Most Arm design and production is outsourced at commodity silicon foundries
In contrast, x86 CPUs must be backwards compatible with older x86 software, requiring retention of legacy hardware not needed by modern software. This raises costs.
x86 chips also tend to be manufactured by the designers themselves (Intel, AMD) at their own advanced and expensive fabs. Arm chips come from dozens of licensees leveraging cheap foundry capacity.
As a result, Arm chips have a cost advantage that translates to cheaper end products like smartphones, tablets and laptops.
Software Support
x86 has a huge ecosystem advantage thanks to its incumbency in the PC market. It runs all major desktop and server operating systems like Windows, Linux and BSDs. Practically every application is compiled for x86.
In comparison, Arm software support historically lagged far behind. But the dominance of Arm in mobile devices is fixing this. Android, iOS and Linux all run on Arm. Large tech companies are investing heavily in Arm servers too.
The remaining issue is application support. Emulation like Apple’s Rosetta 2 helps, but native Arm binaries are still limited outside of mobile apps. This is improving rapidly but will take time to reach parity with x86.
Security
Arm offers a security advantage thanks to its clean architecture unburdened by decades of legacy cruft in x86. The barebones RISC ISA makes it easier to isolate components for greater security.
Arm also mandates use of several security features like TrustZone and architectural mitigations for Spectre/Meltdown-style attacks. Hardware-based security is a key focus for Arm.
In contrast, x86 accumulates technical debt across generations to ensure backwards compatibility. This results in a larger and more complex attack surface. Mitigating vulnerabilities like Spectre is also harder.
So while no architecture is bulletproof, Arm’s modern design and mandatory security features give it a leg up vs the legacy baggage in x86.
Future Trajectory
Arm is expected to continue making big strides and eating into areas traditionally dominated by x86 like laptops and servers. Arm’s power efficiency advantage only grows as Moore’s law slows down.
x86 will retain an advantage in top-end desktops and supercomputers where peak performance trumps all else. Intel and AMD also keep innovating on x86 performance and efficiency.
But for other use cases, Arm’s momentum looks very strong. Qualcomm, Amazon, Microsoft and others are betting big on Arm for the future of computing.
The rise of OS-agnostic platforms like the web and cross-platform apps also erodes x86’s ecosystem advantage. The future will likely belong to both architectures playing to their respective strengths.
Conclusion
There are valid arguments for both Arm and x86. x86 is better for raw CPU performance, while Arm excels at power efficiency. x86 enjoys wider software support today, but Arm is catching up among mobile and web apps. Neither architecture is going away anytime soon.
The bottom line is to go with x86 for desktops/laptops today, and Arm for mobile devices. But pay attention to the rapid improvements in Arm performance as the lines continue to blur between the two architectures.
