Information Technology Reference
In-Depth Information
semination of its new technologies hinged upon the availabil-
ity of hardware and software tools that would allow engineers
to experiment with the new approach to systems design using
microprocessors and
EPROM
s, and would permit complete in-
house development of microprocessor applications.
In mid-1971, Intel's Applications Research Group under the
management of Marcian E. (Ted) Hoff, Jr, the main architect
of Intel's first microprocessor - the 4004 - was given the task
of working closely with the marketing team to assist in promot-
ing both the microprocessor and the
EPROM
. The 4004 micro-
processor, originally designed as a central processing unit (or
CPU
) for digital desktop calculators, could be used effectively in
many applications outside the confines of the calculator market.
In 1971, Intel was facing a considerable marketing challenge to
get this message across.
Hoff's group came to the conclusion that the best way to
showcase the new devices was to use the 4004 microprocessor
to execute programs stored in
EPROM
s. There was one tech-
nical problem, however: the 4004 was designed to work with
a very specific type of
ROM
and was unable to communicate
directly with
EPROM
s. In short, the 4004 required some addi-
tional interface circuitry to allow
EPROM
s to replace the
ROM
s
that the 4004
CPU
was designed to work with. These interface
boards were designed by Applications Research engineers in
mid-1971. “If I remember correctly,” said Hoff, “we developed
them originally for our own use. The 4004 normally worked
with mask-programmed
ROM
, and we developed a board with
an interface that allowed us to use
EPROM
s instead of the 4001
mask-programmed
ROM
.”
The
EPROM
interface board developed by Hoff's group soon
evolved into the
SIM
4-01 prototyping aid that used
EPROM
s
for the development, debugging, and testing of application pro-
grams written for the 4004-based systems. The
SIM
4-01 was a
small printed circuit board measuring 8.4 by 5.7 inches. It had
sockets to hold a 4004 processor, four
RAM
chips (to store a
