Hardware Reference
In-Depth Information
mobile applications such as PDAs. They produced the StrongARM design, which
from its first appearance sent waves through the industry due to its high speed (233
MHz) and ultralow power demands (1 watt). It gained efficiency through a simple,
clean design that included two 16-KB caches for instructions and data. The Stron-
gARM and its successors at DEC were moderately successful in the marketplace,
finding their way into a number of PDAs, set-top boxes, media devices, and rout-
ers.
Perhaps the most venerable of the ARM architectures is the ARM7 design,
first released by ARM in 1994 and still in wide use today. The design included sep-
arate instruction and data caches, and it also incorporated the 16-bit Thumb in-
struction set. The Thumb instruction set is a shorthand version of the full 32-bit
ARM instruction set, allowing programmers to encode many of the most common
operations into smaller 16-bit instructions, significantly reducing the amount of
program memory needed. The processor has worked well for a wide range of low-
to middle-end embedded applications such as toasters, engine control, and even the
Nintendo Gameboy Advance hand-held gaming console.
Unlike many computer companies, ARM does not manufacture any microproc-
essors. Instead, it creates designs and ARM-based developer tools and libraries,
and licenses them to system designers and chip manufacturers. For example, the
CPU used in the Samsung Galaxy Tab Android-based tablet computer is an ARM-
based processor. The Galaxy Tab contains the Tegra 2 system-on-chip processor,
which includes two ARM Cortex-A9 processors and an Nvidia GeForce graphics
processing unit. The Tegra 2 cores were designed by ARM, integrated into a sys-
tem-on-a-chip design by Nvidia, and manufactured by Taiwan Semiconductor
Manufacturing Company (TSMC). It's an impressive collaboration by companies
in different countries in which all of the companies contributed value to the final
design.
Figure 1-14 shows a die photo of the Nvidia's Tegra 2 system-on-a-chip. The
design contains three ARM processors: two 1.2-GHz ARM Cortex-A9 cores plus
an ARM7 core. The Cortex-A9 cores are dual-issue out-of-order cores with a
1-MB L2 cache and support for shared-memory multiprocessing. (That's a lot of
buzzwords that we will get into in later chapters. For now, just know that these fea-
tures make the design very fast!) The ARM7 core is an older and smaller ARM
core used for system configuration and power management. The graphics core is a
333-MHz GeForce graphics processing unit (GPU) design optimized for low-pow-
er operation. Also included on the Tegra 2 are a video encoder/decoder, an audio
processor and an HDMI video output interface.
The ARM architecture has found great success in the low-power, mobile and
embedded markets. In January 2011, ARM announced that it had sold 15 billion
ARM processors since its inception, and indicated that sales were continuing to
grow. While tailored for lower-end markets, the ARM architecture does have the
computational capability to perform in any market, and there are hints that it may
be expanding its horizons. For example, in October 2011, a 64-bit ARM was
