Hardware Reference
In-Depth Information
The fourth generation of the modern computer includes those that incorporate microprocessors in their
designs. Of course, part of this fourth generation of computers is the personal computer, which itself
was made possible by the advent of low-cost microprocessors and memory.
Birth of the Personal Computer
In 1973, some of the first microcomputer kits based on the 8008 chip were developed. These kits
were little more than demonstration tools and didn't do much except blink lights. In April 1974, Intel
introduced the 8080 microprocessor, which was 10 times faster than the earlier 8008 chip and
addressed 64KB of memory. This was the breakthrough that the personal computer industry had been
waiting for.
A company called MITS introduced the Altair 8800 kit in a cover story in the January 1975 issue of
Popular Electronics . The Altair kit, considered by many to be the first personal computer, included
an 8080 processor, a power supply, a front panel with a large number of lights, and 256 bytes (not
kilobytes) of memory. The kit sold for $395 and had to be assembled. Assembly back then meant you
got out your soldering iron to actually finish the circuit boards—not like today, where you can
assemble a system of premade components with nothing more than a screwdriver.
Note
Micro Instrumentation and Telemetry Systems was the original name of the company founded in
1969 by Ed Roberts and several associates to manufacture and sell instruments and transmitters
for model rockets. Ed Roberts became the sole owner in the early 1970s, after which he
designed the Altair. By January 1975, when the Altair was introduced, the company was called
MITS, Inc., which then stood for nothing more than the name of the company. In 1977, Roberts
sold MITS to Pertec, moved to Georgia, went to medical school, and became a practicing
physician. Considered by many to be the “father of the personal computer,” Roberts passed
away in 2010 after a long bout with pneumonia.
The Altair included an open architecture system bus later called the S-100 bus, so named because it
became an industry standard and had 100 pins per slot. The S-100 bus was widely adopted by other
computers that were similar to the Altair, such as the IMSAI 8080, which was featured in the movie
WarGames . The S-100 bus open architecture meant that anybody could develop boards to fit in these
slots and interface to the system, and it ensured a high level of cross-compatibility between different
boards and systems. The popularity of 8080 processor-based systems inspired software companies to
write programs, including the CP/M (control program for microprocessors) OS and the first version
of the Microsoft BASIC (Beginners All-purpose Symbolic Instruction Code) programming language.
IBM introduced what can be called its first personal computer in 1975. The Model 5100 had 16KB of
memory, a built-in 16-line-by-64-character display, a built-in BASIC language interpreter, and a
built-in DC-300 cartridge tape drive for storage. The system's $8,975 price placed it out of the
mainstream personal computer marketplace, which was dominated by experimenters (affectionately
referred to as hackers ) who built low-cost kits ($500 or so) as a hobby. Obviously, the IBM system
was not in competition for this low-cost market and did not sell as well by comparison.
The Model 5100 was succeeded by the 5110 and 5120 before IBM introduced what we know as the
IBM Personal Computer (Model 5150). Although the 5100 series preceded the IBM PC, the older
systems and the 5150 IBM PC had nothing in common. The PC that IBM turned out was more closely
 
 
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