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46 CHAPTER 2 / COMPUTER EVOLUTION AND PERFORMANCE

• Pentium III: The Pentium III incorporates additional floating-point instruc-
tions to support 3D graphics software.
• Pentium 4: The Pentium 4 includes additional floating-point and other en-
hancements for multimedia. 8
• Core: This is the first Intel x86 microprocessor with a dual core, referring to
the implementation of two processors on a single chip.
• Core 2: The Core 2 extends the architecture to 64 bits. The Core 2 Quad pro-
vides four processors on a single chip.
Over 30 years after its introduction in 1978, the x86 architecture continues to
dominate the processor market outside of embedded systems.Although the organiza-
tion and technology of the x86 machines has changed dramatically over the decades,
the instruction set architecture has evolved to remain backward compatible with ear-
lier versions.Thus, any program written on an older version of the x86 architecture can
execute on newer versions.All changes to the instruction set architecture have involved
additions to the instruction set, with no subtractions. The rate of change has been the
addition of roughly one instruction per month added to the architecture over the
30 years [ANTH08], so that there are now over 500 instructions in the instruction set.
The x86 provides an excellent illustration of the advances in computer hard-
ware over the past 30 years. The 1978 8086 was introduced with a clock speed of
5 MHz and had 29,000 transistors. A quad-core Intel Core 2 introduced in 2008 op-
erates at 3 GHz, a speedup of a factor of 600, and has 820 million transistors, about
28,000 times as many as the 8086. Yet the Core 2 is in only a slightly larger package
than the 8086 and has a comparable cost.

2.4 EMBEDDED SYSTEMS AND THE ARM

The ARM architecture refers to a processor architecture that has evolved from
RISC design principles and is used in embedded systems. Chapter 13 examines
RISC design principles in detail. In this section, we give a brief overview of the con-
cept of embedded systems, and then look at the evolution of the ARM.

Embedded Systems
The term embedded system refers to the use of electronics and software within a
product, as opposed to a general-purpose computer, such as a laptop or desktop sys-
tem.The following is a good general definition: 9

Embedded system. A combination of computer hardware and software, and perhaps
additional mechanical or other parts, designed to perform a dedicated function. In many
cases, embedded systems are part of a larger system or product, as in the case of an
antilock braking system in a car.

8 With the Pentium 4, Intel switched from Roman numerals to Arabic numerals for model numbers.
9 Michael Barr,Embedded Systems Glossary.NetrinoTechnical Library.http://www.netrino.com/Publications/
Glossary/index.php