ARM chips account for over 95 per cent of
the mobile market, but why? Let's analyze the ARM and x86 architectures
Intel is the undisputed leader of the
desktop and laptop CPU market, with the most recent figures estimating that
80.2 percent of all processor shipments come from the company. In the embedded
and low-power market, however, it's a bit player: chips based on designs from
ARM, a British company born out of the ashes of Acorn Computers, account for
the overwhelming majority of processors in the mobile market.
Intel isn't comfortable with this
situation, and the company has made significant moves in recent years to
assault the mobile market from the unfamiliar position of the underdog. The
differences between ARM and Intel are far greater than those between Intel and
its nearest desktop rival, AMD; they also extend beyond different business
practices to the very architecture on which the processors are based. But what
difference does it make to the consumer?
The origins of ARM
ARM Holdings, the company responsible for
the architecture that's proved so successful for low-power devices, wasn't
always known as ARM. Launched as an in-house project to create a custom
processor for British micro computing pioneer Acorn, Acorn RISC Machines (later
rebadged as Advanced RISC Machines when Acorn was delisted from the stock
exchange after the great microcomputer crash of 1984) was incorporated in
1990asajointventure between Acorn, Apple and VLSI Technology.
ARM's primary design point, and the focus
for lead engineer Sophie Wilson, was to create low-power, energy-efficient CPUs
as a response to what was seen as the wasteful design of rival chips from
companies such as Motorola and Intel. Despite industry-leading innovations, the
first ARM chips weren't a commercial success; Acorn's Archimedes and RiscPC
product lines would use the chips, but only Digital Equipment Corporation (DEC)
would license the technology. Even Apple, a partner in the ARM project, refused
to use the chip in its desktop computers.
ARM chips' simplified design and reduced
instruction set computer (RISC) architecture meant that they drew significantly
less power than rival processors, however, and as companies started to develop
personal digital assistants (PDAs), and other precursors to today's tablets and
smartphones, the chips looked increasingly tempting. Fast forward to today/,
and ARM boasts a market share in smartphones and tablets of over 95 percent,
while having almost zero presence elsewhere - exactly the opposite of Intel.
ARM'S advantages
ARM's
processor designs are becoming increasingly complex, while Intel's Atom grows
simpler.
However, what makes ARM's designs so
popular for low-power computing? The company certainly has a different approach
to the market from that of Intel, where the latter produces its own chips; ARM
produces no physical goods whatsoever. Instead, it licenses its intellectual
property (IP) to third parties who can either start building ARM-based
processors immediately using an off-the-peg design, or build on ARM's work to
create a custom chip. ARM's licensees include Apple, Marvell, Nvidia, Texas
Instruments, and at one point, even Intel itself.
A simple difference in tactics can't
account for ARM's stellar success, however. Perhaps the biggest contributor to
ARM's domination of the mobile market comes from the architecture itself. Based
on a reduced instruction set, Wilson and his colleague Steve Furber tried to
replicate the efficiency of MOS Technology's 6502chip, which had a more
streamlined approach than that of complex instruction set computer (CISC)
competitors used by Intel. In short, fewer instructions means fewer
transistors.
While Intel's 80286 design packed 134,000
transistors, the first production ARM processordesign-ARM2- outperformed it
with just 30,000 transistors.
Fewer transistors also mean a cheaper,
smaller chip, and these are key considerations in mobile computing. Fewer
transistors also mean a lower power draw, with extended battery life far beyond
what can be offered by a CISC- based design using a similar manufacturing
process.
ARM, through its multifarious licensees,
was also an early adopter of the concept of system-on-chip (SoC) design. Where
a traditional processor requires multiple supporting components, such as the
Northbridge and Southbridge, an SoC packs as much of this as possible into a
single chip. By allowing manufacturers to concentrate on the user-facing
elements of design, while simply dropping in a single chip that handles central
processing, graphics processing, bus processing, communications and more, ARM
became the simplest chip setup on the market. Although some manufacturers still
prefer to produce pure or near-pure ARM CPUs, heavily integrated SoC designs
such as those from Qualcomm account for a large chunk of the market.
Intel fights back
Intel's
decision to create an Atom SoC design gives it major competition to pitch
against ARM's IP
Intel is no stranger to the advantages of
ARM's RISC-based design, of course. As part of a lawsuit settlement with DEC,
Intel gained an ARM licence and used it to produce its StrongARM processors for
the early PDA and embedded markets. That licence would later be sold to
Marvell, with Intel preferring to concentrate on its own x86 architecture.
For a long time, Intel allowed ARM to
dominate the low-power embedded market, but in the past few years the company
has been hitting back. Although originally designed for the netbook market,
Intel's Atom processors-x86 CISC chips designed for low-power usage - are being
pitched as a major competitor to ARM's designs in the burgeoning tablet and
smartphone markets. Its most recent Atom product, the Atom 'Medfield' Z2460, is
a SoC that's already won support in smartphones and tablets from Lenovo, Asus
and Acer.
Intel's attempt to fight back against ARM
has been helped by a shift in processor design: where olderx86 chips were pure
CISC designs, modern chips have more in common with the RISC methodology
preferred by ARM, with a CISC overlay used to provide compatibility with
existing x86 code. As a result, Intel can shrink its designs considerably/, and
while it's unlikely drop to the price of a rival ARM chip, Intel also has huge
cash reserves on its side.
ARM's licensing model means that, despite
its huge popularity, it has razor-thin margins. ARM's revenue for the last
quarter was $314.1 million, while Intel's was $12.45 billion over the same
period. ARM's licensing model means significantly lower operating costs, of
course, but the result is clear in the profit figures:
$92.85 million compared to Intel's $2.55
billion. That extra cash gives Intel the room to invest in research and
development, which is slowly but surely bringing the company close to parity
with its British rival.
The current market
Intel is cagey about detailing the number
of transistors in its Atom Z2460 SoC, but we know it has a 12x12mm
package-on-package (PoP) design. That proves Intel can shrink its parts enough
to compete with companies such as Samsung, which makes a series of 12 x 12mm
ARM parts in the Exynos family; Qualcomm was managing 14 x 14mm packages when
it used a 45nm process for its Snapdragon S1 family.
Intel's
new Atom SoCs are expected to gain a small but important
foothold in the mobile market
Intel still has some way to go, however.
The current-generation Atom SoC might be a similar size to its ARM-based
counterparts, but this was achieved by cutting a few corners. Where Samsung's
Exynos parts are dual- or quad-core, the Atom Z2640 has just one core. Although
dual-core parts are due from Intel, it hasn't yet revealed their size, or what
effect the extra core will have on power draw.
While Intel is working on shrinking its
parts and developing competitive SoC designs, ARM is looking to break into
Intel's primary market. The latest ARMv8 instruction set introduces 64-bit
support for the first time, along with hardware virtualization instructions and
other features that make it suitable for use in servers. With the growth of
cloud computing spurring interest in so-called micro servers, Intel could be
fighting off ARM in its most profitable market, even as it tries to break into
ARM's mobile stronghold. In short, ARM's designs are becoming more complex,
while Intel is simplifying its own. The lines between RISC and CISC have never
been so blurred.
