of Microprocessors

MICROPROCESSORS 127
the size of the memories and I/o system provided and the difficulty or
impossibility of expansion make them special-purpose devices unsuited for
most general-purpose computer applications. However, they do have significant
potential in music synthesis, which will be shown later.
A microcomputer system is a microcomputer with actual 110 devices
added. The ease of use and ultimate potential of the system is strongly related
to the speed and type of I/O equipment present. Also, the majority of the
cost of the system is due to 110 gear. A general-purpose system is one with a
sufficient software and 110 complement to be easily used for many types of
applications. For most work, this simply means that the system has program
development capability, program assembly or compilation capability, and
program execution capability. For many of the musical applications of
microprocessors that will be discussed, a general-purpose system is a
necessity.
Brief History of Microprocessors
Although the history of microprocessors has been short, it has been very
interesting. Reviewing their history here is relevant because it gives an idea
of what to expect for the future. This is important in music synthesis because
today's large computer techniques will be implemented on tomorrow's personal
microcomputer. The dates given in this synopsis are not the manufacturer's
official introduction dates but rather the approximate dates of
availability of the devices to individuals and small businesses. Larger companies
undoubtedly had access to information and prototype chips well before
general availability.
The microprocessor started out as just an ordinary calculator chip that
was documented well enough by the manufacturer so that customers could
program it. Its initial use was simply to expedite the development of
specialized hand-held calculators and business machines such as cash registers.
Shordy thereafter, the semiconductor manufacturers realized that,
whenever a microprocessor chip was sold, memory Ies to hold the programs
were also sold. In fact, it was often the case that more money was spent on
memory than the microprocessor. Thus, the expense ofdeveloping ever more
sophistlcated microprocessor chips was justified on the expectation of increased
profits from memory device sales!
The First True Microprocessor
The first well publicized true microprocessor was the 4004 from Intel,
first available in early 1972. "True" here means a device that works primarily
in the binary number system; is at least theoretically infinitely expandable in
program memory size, data memory size, and 1/0 capability; and can handle
text characters as easily as numbers. Such a device could, if the necessary