The world's first semiconductor companies designed and manufactured chips. Intel still adheres to this model, manufacturing its processors at Intel-owned fabs (industry jargon for fabrication plants), mainly in Arizona and Oregon.
Although AMD originally worked in the same way, it is now a fabless semiconductor company. This means that, although it designs and markets microprocessors, it subcontracts the manufacturing to a so-called silicon foundry.
ARM Holdings is even further removed from real-world products since, although it designs processors, it neither manufactures silicon chips nor markets ARM-branded hardware. Instead it sells, or more accurately licences, intellectual property (IP), which allows other semiconductor companies to manufacture ARM-based hardware.
These chips might be microprocessors as we understand the word, but alternatively they could be complicated chips that form the basis of a mobile phone, for example, of which the ability to execute software is just one element. So in buying the rights to manufacture an ARM-based product, exactly what does a semiconductor manufacturer receive?
We put this question to Ed Plowman, technical marketing manager at ARM's Media Processing Division. "Originally the predominant mode of delivery was via hard macros," he told us. "This is a definition the chip's layout - what to deposit where, and how to connect it all together to make a working circuit".
Over time though, as the number of transistors in the chips increased, along with the number of processes by which each could be manufactured, this became impractical. Designs are now mainly supplied as a circuit description, from which the manufacturer creates a physical design to meet the needs of its own manufacturing processes.
But this data isn't supplied as a circuit diagram - it's provided in a hardware description language that provides a textual definition of how the building blocks connect together. The language used is RTL (register transfer-level), which means, as Ed says, "the definition isn't at the transistor level, but defines how data flows between registers".
This isn't an area where one size fits all, though. ARM sometimes still chooses to implement a hard macro to improve time to market and optimised solutions for certain high-volume process technology nodes.
This is the way, for example, that the Osprey (dual-Cortex-A9) is delivered so pretty much all the manufacturer has to do is create the masks.
Processor and cores
To most technically-minded PC users, a processor is the large component that sits on the motherboard, and which forms the heart of the PC. A core, on the other hand, of which there might be two, four, six or eight, is a part of a processor that's responsible for executing instructions.
Within ARM, though, the two terms have a somewhat different meaning. A processor is pretty much what most people would expect - a design containing all the usual elements, including one or more cores, cache memories and the bus interface.
As such, it's a design that a semiconductor manufacturer can turn directly into a standard silicon component. So, for example, several companies including Toshiba, NEC and TI have ARM Cortex-A9 processors.
A core, on the other hand, is the heart of a microprocessor that semiconductor manufacturers can build into their own custom chip designs. That customised chip will often be much more than what most people would think of as a processor, and could provide a significant proportion of the functionality required in a particular device.
Referred to as a system on silicon (SoC) design, this type of chip minimises the number of components, which, in turn, keeps down both the cost and the size of the circuit board, both of which are essential for high volume portable products such as smartphones.
A perfect example of the increasing amount of functionality that's being shoe-horned into a single chip is the Samsung Exynos 4210 SoC. Intended for smartphones, tablet PCs and netbooks, the chip features a 1.2GHz dual-core ARM Cortex-A9, plus just about everything that would be found as separate chips on the motherboard on a conventional PC.
For example, there's on-chip 3D graphics and audio hardware, 1080p video encode and decode, plus interfaces for the display, camera and keypad. There are also memory, USB, PCI Express (expansion card), SATA (hard disk) and memory card interfaces and, while the necessary RF (radio frequency) circuitry would have to be provided by a separate chip, there's support for the various communication channels including Wi-Fi, HSPA+ and LTE (3G and 4G mobile phone) and GPS.
We've seen that ARM processors and cores are used in hand-held and portable devices like smartphones, tablet PCs and netbooks, but this is only the tip of the iceberg.
As Ed Plowan put it, "You can walk around any branch of stores like Comet or Curry's and be falling over ARM devices, but you won't know it." Included here are the likes of games consoles, personal media players, set-top boxes, internet radios, home automation systems, GPS receivers, ebook readers, TVs, DVD and Blu-ray players, digital cameras and home media servers.
Cheaper, less powerful chips are found in less likely sounding home products, including toys, cordless phones and even coffee makers. There's a good chance that your car could contain a fair few ARM-based devices too. They're used to drive dashboard displays, anti-lock breaking, airbags and other safety-related systems, and for engine management.
Ed also mentioned healthcare products as a major growth area over the last five years, with products varying from remote patient monitoring systems to medical imaging scanners. While your desktop or laptop PC won't feature an ARM chip as its main processor, there's a good chance that there'll be one or more hidden away somewhere doing some unexpected but important job.
ARM devices are used extensively in hard disk and solid state drives. They also crop up in wireless keyboards, and are used as the driving force behind printers and networking devices like wireless router/access points.
Before you jump to the conclusion that ARM products are destined to play a supporting role in traditional computing platforms indefinitely, we really ought to mention the EU Mont-Blanc Project.
With the aim of providing high performance computing but without the high energy consumption of today's top supercomputers, project partner the Barcelona Computing Centre is building a supercomputer from ARM-based Nvidia Tegra processors. As yet there's no indication of how many thousand of these chips will be used and what level of performance will be achieved, but this first ARM-based supercomputer will certainly break new ground in terms of energy efficiency.
While the initial goal is to provide two to five times the efficiency of x64-based supercomputers, this is expected to increase to as much as 10 times by 2014 and the ultimate project aim is a 10-30 fold improvement.