Hardware Reference
In-Depth Information
pay a few million dollars once in a while for a new one, than to even contemplate
the effort required to reprogram all their applications for smaller machines.
It is this class of computer that led to the now-infamous Year 2000 problem,
which was caused by (mostly COBOL) programmers in the 1960s and 1970s
representing the year as two decimal digits (in order to save memory). They never
envisioned their software lasting three or four decades. While the predicted disas-
ter never occurred due to a huge amount of work put into fixing the problem, many
companies have repeated the same mistake by simply adding two more digits to the
year. The authors hereby predict the end of civilization at midnight on Dec. 31,
9999, when 8000 years worth of old COBOL programs crash simultaneously.
In addition to their use for running 40-year-old legacy software, the Internet
has breathed new life into mainframes. They have found a new niche as powerful
Internet servers, for example, by handling massive numbers of e-commerce
transactions per second, particularly in businesses with huge databases.
Up until recently, there was another category of computers even more powerful
than mainframes:
supercomputers
. They had enormously fast CPUs, many giga-
bytes of main memory, and very fast disks and networks. They were used for mas-
sive scientific and engineering calculations such as simulating colliding galaxies,
synthesizing new medicines, or modeling the flow of air around an airplane wing.
However, in recent years, data centers constructed from commodity components
have come to offer as much computing power at much lower prices, and the true
supercomputers are now a dying breed.
In this topic we will focus on three popular instruction set architectures (ISAs):
x86, ARM and AVR. The x86 architecture is found in nearly all personal com-
puters (including Windows and Linux PCs and Macs) and server systems. Personal
computers are of interest because every reader has undoubtedly used one. Servers
are of interest because they run all the services on the Internet. The ARM architec-
ture dominates the mobile market. For example, most smartphones and tablet com-
puters are based on ARM processors. Finally, the AVR architecture is found in
very low-cost microcontrollers found in many embedded computing applications.
Embedded computers are invisible to their users but control cars, televisions,
microwave ovens, washing machines, and practically every other electrical device
costing more than $50. In this section, we will briefly introduce the three instruc-
tion set architectures that will be used as examples in the rest of the topic.
In 1968, Robert Noyce, inventor of the silicon integrated circuit; Gordon
Moore, of Moore's law fame; and Arthur Rock, a San Francisco venture capitalist,
formed the Intel Corporation to make memory chips. In its first year of operation,
