of Microprocessors

128 MUSICAL ApPLICATIONS OF MICROPROCESSORS
effort were expended, be programmed to handle any kind of computer task
except at a slower speed. Intel marketed the 4004 strictly as logic replacement
where speed was not important but logic decision complexity was high
such as in traffic light controllers or automatic bowling pin setters. The 4-bit
word size, instruction set, and data memory-addressing method utilized by
the 4004, however, seemed quite strange to those already familiar with miniand
maxicomputers, so they did not show much interest in using the device
for conventional computer applications. Another inhibition to its use by
individuals and small enterprises was the virtual requirement that
specialized, mask-programmed I memory components from Intel be used.
The First Popular Microprocessor
Several months later, Intel made available the 8008 microprocessor.
This 8-bit machine overcame many of the problems of the 4004. It was
designed to be usable with standard memory components from a variety of
manufacturers. Its method of addressing memory was much more conventional
with program and data memory being identical. Also, it could directly
address without bank switching 16K bytes, an amount considered ample at
the time. Its instruction set was definitely limited but conventional enough
to be identified with the instruction sets of the smaller minicomputers. The
major limitations of the 8008 were slow speed and a rudimentary interrupt
capability.
This air of conventionality and familiarity, however, was the key to its
success and, in the opinion of some, the cause of sooner-than-expected use of
microprocessors as minicomputer replacements in many applications. What
was actually being offered was not a cheaper way to make traffic light
controllers but a computer, with all of the capabilities and potential of other
much more expensive computers. People knowledgeable about computers
realized this and acted on it. University electrical engineering, chemical
engineering, and computer science departments launched microcomputer
projects so that each student could work with a real computer in lab sessions.
Entrepreneurs dreamed up small microcomputer-based systems and immediately
set out to develop them. Hard-core hobbyists started building their
own computers around the 8008. The semiconductor manufacturers found
customers writing huge, complex programs and adding extra outboard logic
to the microprocessor to overcome the weaknesses that still remained.
The Dawn ofPersonal Computing
One event of major significance was the publication in one of the major
hobby electronics magazines in March 1974 of an article describing a build-
1A mask-programmed memory device incurs a tooling charge of $750 to $2,000 and a
minimum order of 25 copies or more. Any change ro the program requires a new
mask. Thus, such a technique is only suitable for large-quantity production.