ARM Architecture

ARM Architecture

The ARM architecture describes a family of computer processors designed in accordance with a RISC CPU design developed by British company ARM Holdings. ARM architecture has been in development since the 1980s and is the most widely used 32-bit instruction set architecture, in numbers produced. ARM was an acronym for Advanced RISC Machine (previously known as Acorn RISC Machine).

Using the RISC approach, the core ARM processor requires only 35,000 transistors, compared to the millions in many conventional processor chips, resulting in lower power usage and making it very attractive in smaller devices. The company ARM Holdings does not manufacture its own electronic chips, but assigns different licenses to semiconductor manufacturers. It is thus easy for companies to build a low-energy system on a chip for an embedded system incorporating memory, interfaces, radios, etc. The earliest example was the Apple Newton tablet but this same approach is still used in the Apple A4 and A5 chips in the iPad.

In 2011, ARM's customers reported 7.9 billion ARM processors shipped, representing 95% of smartphones, 90% of hard disk drives, 40% of digital televisions and set-top boxes, 15% of microcontrollers and 20% of mobile computers. Current versions use 32-bit instructions with 32-bit addressed 1 byte wide memory which is effectively reduced to just over 24 bit addressing due to 4 byte alignment, with some addressing reserved in byte wise allocation for Memory Mapped I/O, but accommodates 16-bit instructions for economy and can also handle Java bytecodes which use 32-bit addresses. In 2012, Microsoft produced its new Surface tablet with ARM technology and AMD announced that it would start producing server chips based on the 64-bit ARM core in 2014.