Understanding ARM
Here is a summary of the history and evolution of ARM architecture:
Origins at Acorn Computers
- In the early 1980s, British company Acorn Computers needed a processor for their new Acorn Archimedes computer that could deliver high performance while being energy efficient.
- This led to the creation of the first ARM processor, the ARM1, in 1985. It was designed by Sophie Wilson and Steve Furber.
- The ARM architecture was based on Reduced Instruction Set Computer (RISC) principles, using a small set of instructions that could be executed quickly. This made it simpler and more power-efficient compared to Complex Instruction Set Computer (CISC) designs at the time.
- The ARM2, released in 1987, added a Booth multiplier and a Fast Interrupt reQuest (FIQ) mode. It offered performance comparable to contemporary workstations while drawing less power.
Early Licensees and Market Share Growth
- In 1990, ARM was officially founded as a joint venture between Acorn, Apple, and VLSI Technology.
- ARM introduced the IP licensing business model, allowing partners to license the ARM architecture and produce their own ARM-based chips.
- Early licensees included Texas Instruments, who used ARM in Nokia’s GSM mobile phones in the 1990s.
- By 2005, about 98% of mobile phones used at least one ARM processor. By 2010, ARM had shipped 6.1 billion processors, with 95% in smartphones.
ARMv7 Architecture
The ARMv7 architecture, introduced in 2006, defines three main profiles:
ARMv7-A (Application): Designed for high-performance applications like smartphones, tablets, and servers. It supports a 32-bit instruction set and virtual memory management.
ARMv7-R (Real-Time): Optimized for real-time systems with deterministic behavior, such as industrial control and automotive applications. It supports a 32-bit instruction set and a Memory Protection Unit (MPU).
ARMv7-M (Microcontroller): Focused on low-power, cost-sensitive embedded systems. It supports a 32-bit Thumb instruction set and a simplified programmers’ model compared to ARMv7-A and ARMv7-R.
Notable ARMv7 processors include the Cortex-A8, Cortex-A9, Cortex-R4, and Cortex-M3.
ARMv8 Architecture
The ARMv8 architecture, introduced in 2011, added support for 64-bit processing. It defines three main profiles:
ARMv8-A (Application): Extends the ARMv7-A profile with a new 64-bit instruction set (AArch64) and 64-bit registers. It also retains support for the 32-bit instruction set (AArch32) for backward compatibility.
ARMv8-R (Real-Time): Extends the ARMv7-R profile with some ARMv8-A features, including 64-bit support.
ARMv8-M (Microcontroller): Extends the ARMv7-M profile with additional security features and support for the Thumb instruction set.
Notable ARMv8-A processors include the Cortex-A53, Cortex-A57, and Cortex-A72. ARMv8-M processors include the Cortex-M23 and Cortex-M33.
ARM64 (AArch64)
ARM64, also known as AArch64, is the 64-bit instruction set architecture introduced with ARMv8-A. It provides:
- 31 general-purpose 64-bit registers
- 32 floating-point/SIMD 128-bit registers
- 4 GB exception levels for hardware virtualization and security
- 48-bit virtual address space (can be extended to 52 bits)
- Improved performance and energy efficiency compared to 32-bit ARM
ARM64 is used in high-performance applications like servers, HPC, and flagship mobile devices. Examples include the Cortex-A57, Cortex-A72, and Neoverse N1 processors.
Expansion into New Markets
- ARM’s architecture expanded beyond mobile into markets like automotive, IoT, servers, and supercomputers.
- The Neoverse family targeted server and cloud computing workloads.
- By 2022, 65% of embedded IoT devices used ARM-based chips.
Acquisition by SoftBank
- In 2016, ARM was acquired by Japanese conglomerate SoftBank for $32 billion.
- This took ARM private after nearly 20 years as a public company.
In summary, ARM’s RISC-based architecture, IP licensing model, and energy-efficient designs have enabled it to grow from a British startup to a dominant force powering a wide range of computing devices globally. Its evolution has allowed it to adapt to the changing needs of the technology industry over the past 35+ years.