Hardware Reference
In-Depth Information
memory words. Together, the arithmetic logic unit and the control unit formed the
''brain'' of the computer. In modern computers they are combined onto a single
chip called the
CPU
(
Central Processing Unit
).
Inside the arithmetic logic unit was a special internal 40-bit register called the
accumulator
. A typical instruction added a word of memory to the accumulator
or stored the contents of the accumulator in memory. The machine did not have
floating-point arithmetic because von Neumann felt that any competent mathemati-
cian ought to be able to keep track of the decimal point (actually the binary point)
in his or her head.
At about the same time von Neumann was building the IAS machine, re-
searchers at M.I.T. were also building a computer. Unlike IAS, ENIAC and other
machines of its type, which had long word lengths and were intended for heavy
number crunching, the M.I.T. machine, the Whirlwind I, had a 16-bit word and was
designed for real-time control. This project led to the invention of the magnetic
core memory by Jay Forrester, and then eventually to the first commercial
minicomputer.
While all this was going on, IBM was a small company engaged in the busi-
ness of producing card punches and mechanical card-sorting machines. Although
IBM had provided some of Aiken's financing, it was not terribly interested in com-
puters until it produced the 701 in 1953, long after Eckert and Mauchley's com-
pany was number one in the commercial market with its UNIVAC computer. The
701 had 2048 36-bit words, with two instructions per word. It was the first in a
series of scientific machines that came to dominate the industry within a decade.
Three years later came the 704, which initially had 4096 words of core memory,
36-bit instructions, and a new innovation, floating-point hardware. In 1958, IBM
began production of its last vacuum-tube machine, the 709, which was basically a
beefed-up 704.
The transistor was invented at Bell Labs in 1948 by John Bardeen, Walter Brat-
tain, and William Shockley, for which they were awarded the 1956 Nobel Prize in
physics. Within 10 years the transistor revolutionized computers, and by the late
1950s, vacuum tube computers were obsolete. The first transistorized computer
was built at M.I.T.'s Lincoln Laboratory, a 16-bit machine along the lines of the
Whirlwind I. It was called the
TX-0
(
Transistorized eXperimental computer 0
)
and was merely intended as a device to test the much fancier TX-2.
The TX-2 never amounted to much, but one of the engineers working at the
Laboratory, Kenneth Olsen, formed a company, Digital Equipment Corporation
(DEC), in 1957 to manufacture a commercial machine much like the TX-0. It was
four years before this machine, the PDP-1, appeared, primarily because the venture
capitalists who funded DEC firmly believed that there was no market for com-
puters. After all, T.J. Watson, former president of IBM, once said that the world
