How Do x86, ARM, and RISC‑V Architectures Differ? A Deep Dive into CPU Instruction Sets

Overview of Recent Updates

Recent updates cover CPU architecture evolution (Intel/AMD and domestic designs), GPU architecture from Fermi to Hopper, memory, OS and storage technologies, known issue fixes, and more than 40 pages of PPT material.

Instruction Set Architectures (ISA)

Modern processors mainly use two ISA families: the Complex Instruction Set Computing (CISC) x86 family and the Reduced Instruction Set Computing (RISC) families such as ARM, MIPS, Alpha and the open RISC‑V.

1. x86 Instruction Set

x86 maintains binary compatibility across generations, leading to a large and growing instruction set (over 1 600 instructions after nearly 40 years). Its strong instructions can perform complex operations in a single cycle, but this results in hardware complexity, higher power consumption and larger die area.

Compatibility makes the design complex but enables Intel’s dominance in PCs and servers.

Powerful single‑instruction operations reduce compiler requirements.

Parallel high‑efficiency instructions give strong single‑core performance.

Redundant transistors increase area and power overhead.

2. ARM Instruction Set

ARM follows a RISC philosophy, keeping only the most frequently used instructions. It offers three licensing profiles: Cortex‑A for high‑performance, Cortex‑R for real‑time, and Cortex‑M for embedded devices.

Compared with x86, ARM removes many redundant instructions, replaces strong x86 instructions with multiple simple ones, and thus achieves smaller die area and lower power at the cost of higher compiler complexity.

Simpler decode logic reduces area and power.

Single‑purpose instructions lower power per operation.

Multiple simple instructions increase compiler and assembly difficulty.

Smaller cores enable stacking many cores to match x86 performance.

3. RISC‑V Instruction Set

RISC‑V is an open, royalty‑free ISA that has grown from academic research to commercial adoption, especially in IoT, edge, and increasingly in servers and PCs. China’s RISC‑V ecosystem includes several alliances and product releases such as the Xuantie 910 processor.

2018 – China RISC‑V Industry Alliance founded.

2019 – Alibaba’s “Xuantie 910” released.

2023 – RISC‑V China Summit held in Beijing.

2025 – New high‑performance RISC‑V server chip announced.

4. Summary

The choice between CISC (x86) and RISC (ARM, RISC‑V, etc.) depends on application requirements: CISC offers extensive legacy support and powerful single‑instruction capabilities, while RISC provides simpler hardware, lower power, and flexibility for customization.