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ARM architecture family

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Arm is a massive family of instruction set architectures (ISAs) used in computer processors.

ARMSoCBlockDiagram
ARMSoCBlockDiagram

An ISA acts as a set of rules that tells a processor how to perform tasks. Arm Holdings develops these rules and licenses them to other companies. These companies then build the physical hardware that follows the Arm instructions. Because Arm chips use low power and generate little heat, they are ideal for portable devices. You can find them in smartphones, tablets, and laptops. They are also used in massive supercomputers, such as the Fugaku system.

ARMCortexA57A53
ARMCortexA57A53

With over 230 billion chips produced, Arm is the most widely used architecture family in the world.

The Arm design is based on Reduced Instruction Set Computer (RISC) principles. This approach focuses on using a small, efficient set of instructions to keep the hardware simple. The original designers at Acorn used specific methods to increase performance. For example, they used a 26-bit address space to handle interrupts quickly. An interrupt is a signal that tells the processor to stop its current task to handle something else. By limiting the address space, the entire state of the machine could be saved in a single operation. This halved the overhead required to manage interrupts.

GPS ARM610 die
GPS ARM610 die

Another key mechanism involves how the processor communicates with memory. The designers utilized a feature called page mode DRAM. Page mode allows the chip to access memory much faster if the data is in the same location. The Arm architecture includes special memory access instructions known as "S-cycles." These S-cycles allow the processor to fill or save multiple registers within a single memory page. This effectively doubled memory performance in certain tasks. This was especially useful for improving the speed of computer graphics.

The history of Arm began with a company called Acorn Computers. In 1981, Acorn released the BBC Micro, which was very successful. The team wanted to create a new machine with ten times the performance of the BBC Micro. They also wanted to keep the price the same to compete with the IBM Personal Computer. In late 1983, the team decided to design their own CPU. They named it the Acorn RISC Machine. Sophie Wilson developed the instruction set by writing a simulation in BBC BASIC.

Acorn-ARM-Evaluation-System
Acorn-ARM-Evaluation-System

The first working silicon samples were known as the ARM1. These chips were tested and worked correctly on April 26, 1985. The ARM1 ran at a speed of 6 MHz. It was first used as a second processor for the BBC Micro. Later, in late 1986, the team introduced the ARM2 design. This version ran at 8 MHz and was much more powerful. The ARM2 featured a 32-bit data bus and 27 32-bit registers. It also included a Booth multiplier to handle multiplication tasks more efficiently.

The ARM2 was remarkably efficient compared to other chips of its time. It used only 30,000 transistors to function. In comparison, the Motorola 68000 used about 68,000 transistors. Because it had fewer transistors and lacked microcode, the ARM2 used less power. This simplicity allowed it to stay cool without complex thermal packaging. The ARM2 was powerful enough to compete with expensive workstations. It was used in the Acorn Archimedes computers starting in June 1987.

Over the years, the Arm architecture has evolved through many different generations. The original designs were 32-bit, but they had limitations on how much memory they could use. The ARMv3 series removed these limits by providing a full 32-bit address space. In 2011, the ARMv8-A architecture was released. This major update added support for 64-bit arithmetic and a 64-bit address space.

STM32F103VGT6-HD
STM32F103VGT6-HD

This allows modern computers to process much larger amounts of data at once.

There are also specialized versions of the architecture for different roles. The "Thumb" extensions allow for both 32-bit and 16-bit instructions. This improves code density, which helps save memory space. Another extension called Jazelle was added to handle Java bytecode directly. Recent versions have also added simultaneous multithreading (SMT) to improve performance.

Raspberry-Pi-2-Bare-BR
Raspberry-Pi-2-Bare-BR

From tiny embedded systems to the world's fastest supercomputers, Arm technology connects many different fields of science and computing.

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🖼️ Images & Media (8)
File:Acorn-ARM-Evaluation-System.jpg
Acorn-ARM-Evaluation-System.jpg
File:ARMSoCBlockDiagram.svg
ARMSoCBlockDiagram.svg
File:GPS ARM610 die.JPG
GPS ARM610 die.JPG
File:STM32F103VGT6-HD.jpg
STM32F103VGT6-HD.jpg
File:Quad-core Android "mini PC", with a microSD card next to it for a size comparison.jpg
Quad-core Android "mini PC", with a...
File:Raspberry-Pi-2-Bare-BR.jpg
Raspberry-Pi-2-Bare-BR.jpg
File:Cubox.png
Cubox.png
File:ARMCortexA57A53.jpg
ARMCortexA57A53.jpg
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