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The Beginning: Acorn Computers Ltd

May 9th 2020 - 2:22 PM EST - by:@officialchaos Follow

Any British person the age of 30+ will most likely remember Acorn Computers Ltd and the extremely popular BBC Micro (launched with a 6502 processor in 1981).

ARM, previously Advanced RISC Machine, originally Acorn RISC Machine, is a family of reduced instruction set computing (RISC) architectures for computer processors, configured for various environments.

Designed in 1985 and used in most products that implement one of those architectures‍—‌including systems-on-chips (SoC) and systems-on-modules (SoM) that incorporate memory, interfaces, radios, etc. Architecture versions ARMv3 to ARMv7 support 32-bit address space (pre-ARMv3 chips had 26-bit address space) and 32-bit arithmetic; most architectures have 32-bit fixed-length instructions.

Released in 2011, the ARMv8-A architecture added support for a 64-bit address space and 64-bit arithmetic with its new 32-bit fixed-length instruction set. Some recent Arm CPUs have simultaneous multithreading (SMT) with e.g. Arm Neoverse E1 being able to execute two threads concurrently for improved aggregate throughput performance.

ARM Cortex-A65AE for automotive applications is also a multithreaded processor, and has Dual Core Lock-Step for fault-tolerant designs (supporting Automotive Safety Integrity Level D, the highest level). The Neoverse N1 is designed for "as few as 8 cores" or "designs that scale from 64 to 128 N1 cores within a single coherent system".

With over 130 billion ARM processors produced, as of 2019, ARM is the most widely used instruction set architecture (ISA) and the ISA produced in the largest quantity. Currently, the widely used Cortex cores, older "classic" cores, and specialized SecurCore cores variants are available for each of these to include or exclude optional capabilities.