I ntel x86 vs. Arm: Architecture and all key differences explained

ARM Architecture
ARM is RISC (Reduced Instruction Set Computing) based while Intel (x86) is CISC (Complex Instruction Set Computing). Arm’s CPU instructions are reasonably atomic, with a very close correlation between the number of instructions and micro-ops. CISC, by comparison, offers many more instructions, many of which execute multiple operations (such as optimized math and data movement). This leads to better performance, but more power consumption decoding these complex instructions.

Arm introduced its ARMv8 64-bit architecture in 2011. Rather than extend its 32-bit instruction set, Arm offers a clean 64-bit implementation. To accomplish this, the ARMv8 architecture uses two execution states, AArch32 and AArch64. As the names imply, one is for running 32-bit code and one for 64-bit. The beauty of the ARM design is the processor can seamlessly swap from one mode to the other during its normal execution. This means that the decoder for the 64-bit instructions is a new design that doesn’t need to maintain compatibility with the 32-bit era, yet the processor as a whole remains backwardly compatible.
ARM’s win on mobile ecosystem
The architectural differences discussed above partly explain the current successes and issues faced by the two chip behemoths. Arm’s low power approach is perfectly suited to the 3.5W Thermal Design Power (TDP) requirements of mobile, yet performance scales up to match Intel’s laptop chips too. Meanwhile, Intel’s 100W TDP typical Core i7 wins big in servers and high-performance desktops but historically struggles to scale down below 5W.
One unique feature of Arm’s architecture has been particularly instrumental in keeping TDP low for mobile applications, heterogeneous computing. The idea is simple enough, build an architecture that allows different CPU parts (in terms of performance and power) to work together for improved efficiency. Heterogeneous Multiprocessing (HMP) is already big in the Android space, see chips like the Snapdragon 810, Exynos 7420 or Helio X20, but Heterogeneous Compute (HC) is the next evolution.


You see, processors can be designed to perform certain tasks more efficiently, but a single design struggles to be great at everything. Your typical CPU may be good at serial processing, while a GPU can handle streams of parallel data and a DSP is better optimized for crunching numbers to high accuracy in real-time. With a wider range of options to choose from, the theory is that picking the best processor for any specific task will result in better performance and energy efficiency.