IEEE Spectrum September, 2016 - 52

n ThIS SEnSE, it was an electronic calculator that begot the first microprocessor, Intel's
4-bit 4004. But the 8-bit microprocessors that
quickly succeeded it had a very different genesis.
That story starts in 1969 with the development of
the datapoint 2200 "programmable terminal," by
a company called Computer Terminal Corp. (CTC),
based in San antonio, Texas.
The datapoint 2200 was really a general-purpose
computer, not just a terminal. Its 8-bit processor
was initially built out of about 100 bipolar chips.
Its designers were looking for ways to have the processor consume less power and generate less heat.
So in early 1970, CTC arranged for Intel to build a
single MOS chip to replace the datapoint processor board, although it's unclear whether the idea of
using a single chip came from Intel or CTC.
By June 1970, Intel had developed a functional
specification for a chip based on the architecture
of the datapoint 2200 and then put the project on
hold for six months. This is the design that would
become the Intel 8008. So whether you consider the
calculator-inspired 4004 or the terminal-inspired
8008 to be the first truly useful single-chip, generalpurpose microprocessor, you'd have to credit its
creation to Intel, right? not really.
You see, in 1970, when Intel began working on
the 8008, it was a startup with about 100 employees. after learning of Intel's processor project,
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S ThIS hISTOrY MaKES CLEar, the evolution of the microprocessor followed anything but a straight line. Much was the
result of chance and the outcome of various business decisions
that might easily have gone otherwise. Consider how the 8-bit processor architecture that CTC designed for the datapoint 2200 was
implemented in four distinct ways. CTC did it twice using a board
stuffed with bipolar chips, first in an arrangement that communicated data serially and later using a parallel design that was much
faster. Both TI and Intel met CTC's requirements with single chips
having almost identical instruction sets, but the packaging, control
signals, instruction timing, and internal circuitry of the two chips
were entirely different.
Intel used more advanced technology than did TI, most notably selfaligned gates made of polysilicon, which made the transistors faster

From toP: history-comPuter.com; comPuter history museum

CPU FLIP-FLOPS: Makers
of the Datapoint 2200
terminal [above] sought
a single-chip CPU for it
from both Intel and Texas
Instruments. Gary Boone
[left] led the development
of TI's solution to this
challenge. Neither TI nor
Intel's CPU chips saw use
in the Datapoint 2200,
but they led a wave of
8-bit microprocessors
that powered the
microcomputer revolution.

Texas Instruments, or TI-a behemoth of a company, with 45,000
employees-asked CTC whether it, too, could build a processor for
the datapoint 2200. CTC gave engineers at TI the computer's specifications and told them to go ahead. When they returned with a threechip design, CTC pointedly asked whether TI could build it on one
chip, as Intel was doing. TI then started working on a single-chip
CpU for CTC around april 1970. That design, completed the next
year, was first called the TMX 1795 (X for "experimental"), a name
that morphed into TMC 1795 when it was time for the chip to shed
its prototype status.
In June 1971, TI launched a media campaign for the TMC 1795 describing how this "central processor on a chip" would make the new
datapoint 2200 "a powerful computer with features the original
one couldn't offer." That didn't happen, though: after testing the
TMC 1795, CTC rejected it, opting to continue building its processor
using a board of bipolar chips. Intel's chip wouldn't be ready until
the end of that year.
Many historians of technology believe that the TMC 1795 died then
and there. But newly surfaced documents from the late Gary Boone,
the chip's lead developer, show that after CTC's rejection, TI tried to
sell the chip (which after some minor improvements became known
as the TMC 1795a) to various companies. Ford Motor Co. showed interest in using the chip as an engine controller in 1971, causing Boone
to write, "I think we have walked into the mass market our 'CpU-ona-chip' desperately needs." alas, these efforts failed, and TI ceased
marketing the TMC 1795, focusing on its more profitable calculator
chips instead. nevertheless, if you want to assign credit for the first
8-bit microprocessor, you should give that honor to TI, never mind
that it fumbled the opportunity.
By the time Intel had the 8008 working, at the end of 1971, CTC
had lost interest in single-chip CpUs and gave up its exclusive rights
to the design. Intel went on to commercialize the 8008, announcing
it in april 1972 and ultimately producing hundreds of thousands of
them. Two years later, the 8008 spawned Intel's 8080 microprocessor, which heavily influenced the 8086, which in turn opened the
floodgates for Intel's current line of x86 chips. So if you're sitting at a
pC with an x86 processor right now, you're using a computer based
on a design that dates all the way back to datapoint's 2200 programmable terminal of 1969.

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Table of Contents for the Digital Edition of IEEE Spectrum September, 2016