Computer in Use. Маркушевская Л.П - 96 стр.

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Университет ИТМО | Санкт-Петербург

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96
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CENTRAL PROCESSING UNIT
1. A central processing unit (CPU) or processor is the piece of hardware in a
computer that interprets and executes instructions and data contained in software.
Microprocessors are CPUs that are manufactured on integrated circuits, often as a
single-chip package. Since the mid-1970s, these single-chip microprocessors have
become the most common and prominent implementations of CPUs, and today the
term is almost always applied to this form.
2. The term "Central processing unit" is, in general terms, a functional
description of a certain class of programmable logic machines. This broad definition
can easily be applied to many early computers that existed long before the term
"CPU" ever came into widespread usage. The term and its acronym have been in use
at least since the early 1960s.
MICROPROCESSORS
3. An innovation that has significantly affected the design and implementation
of CPUs came in the mid-1970s with the microprocessor. Since the introduction of
the first microprocessor (the Intel 4004) in 1970 and the first widely-used
microprocessor (the Intel 8080) in 1974, this class of CPUs has almost completely
overtaken all other implementations. While the previous generation of CPUs was
integrated as discrete components on one or more circuit boards, microprocessors are
manufactured onto compact integrated circuits (ICs), often a single chip. The smaller
transistor sizes mean faster switching time due to decreased gate capacitance. This
has allowed synchronous microprocessors to utilize clock rates ranging from tens of
megahertz to several gigahertz. Additionally, as the ability to construct exceedingly
small transistors on an IC has increased, the complexity of and number of transistors
in a single CPU has increased dramatically. This trend has been observed by many
and is often described by Moore's law, which has proven to be a fairly accurate model
of the growth of CPU (and other IC) complexity to date.
4. While the complexity, size, construction, and general form of CPUs has
changed drastically over the past sixty years, it is notable that the basic design and
function has not changed much at all. Almost all common CPUs today can be very
accurately described as Von Neumann stored program machines.
5. As the aforementioned Moore's law continues to hold true, concerns about
the limits of integrated circuit transistor technology have become much more
prevalent. Extreme miniaturization of electronic gates is causing the effects of
phenomena like electromigration and subthreshold leakage to become much more
significant. These newer concerns are among the many factors causing researchers to
investigate new methods of computing such as the quantum computer as well as
expand the usage of parallelism and other methods that extend the usefulness of the
classical Von Neumann model.

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