The history of the central processing unit (CPU)

The

central
processing
unit
(CPU)
is
the
computer’s
brain.
It
handles
the
assignment
and
processing
of
tasks,
in
addition
to
functions
that
make
a
computer
run.

There’s
no
way
to
overstate
the
importance
of
the
CPU
to
computing.
Virtually
all
computer
systems
contain,
at
the
least,
some
type
of
basic
CPU.
Regardless
of
whether
they’re
used
in
personal
computers
(PCs),
laptops,
tablets,
smartphones
or
even
in
supercomputers
whose
output
is
so
strong
it
must
be
measured
in
floating-point
operations
per
second,
CPUs
are
the
one
piece
of
equipment
on
computers
that
can’t
be
sacrificed.
No
matter
what
technological
advancements
occur,
the
truth
remains—if
you
remove
the
CPU,
you
simply
no
longer
have
a
computer.

In
addition
to
managing
computer
activity,
CPUs
help
enable
and
stabilize
the
push-and-pull
relationship
that
exists
between
data
storage
and
memory.
The
CPU
serves
as
the
intermediary,
interacting
with
the
primary
storage
(or
main
memory)
when
it
needs
to
access
data
from
the
operating
system’s
random-access
memory
(RAM).
On
the
other
hand,
read-only
memory
(ROM)
is
built
for
permanent
and
typically
long-term
data
storage.

CPU
components

Modern
CPUs
in
electronic
computers
usually
contain
the
following
components:

• 
  Control
  unit:
  Contains
  intensive
  circuitry
  that
  leads
  the
  computer
  system
  by
  issuing
  a
  system
  of
  electrical
  pulses
  and
  instructs
  the
  system
  to
  carry
  out
  high-level
  computer
  instructions.
• 
  Arithmetic/logic
  unit
  (ALU):
  Executes
  all
  arithmetic
  and
  logical
  operations,
  including
  math
  equations
  and
  logic-based
  comparisons
  that
  are
  tied
  to
  specific
  computer
  actions.
• 
  Memory
  unit:
  Manages
  memory
  usage
  and
  flow
  of
  data
  between
  RAM
  and
  the
  CPU.
  Also
  supervises
  the
  handling
  of
  the
  cache
  memory.
• 
  Cache:
  Contains
  areas
  of
  memory
  built
  into
  a
  CPU’s
  processor
  chip
  to
  reach
  data
  retrieval
  speeds
  even
  faster
  than
  RAM
  can
  achieve.
• 
  Registers:
  Provides
  built-in
  permanent
  memory
  for
  constant,
  repeated
  data
  needs
  that
  must
  be
  handled
  regularly
  and
  immediately.
• 
  Clock:
  Manages
  the
  CPU’s
  circuitry
  by
  transmitting
  electrical
  pulses.
  The
  delivery
  rate
  of
  those
  pulses
  is
  referred
  to
  as
  clock
  speed,
  measured
  in
  Hertz
  (Hz)
  or
  megahertz
  (MHz).
• 
  Instruction
  register
  and
  pointer:
  Displays
  location
  of
  the
  next
  instruction
  set
  to
  be
  executed
  by
  the
  CPU.
• 
  Buses:
  Ensures
  proper
  data
  transfer
  and
  data
  flow
  between
  the
  components
  of
  a
  computer
  system.

How
do
CPUs
work?

CPUs
function
by
using
a
type
of
repeated
command
cycle
that
is
administered
by
the
control
unit
in
association
with
the
computer
clock,
which
provides
synchronization
assistance.

The
work
a
CPU
does
occurs
according
to
an
established
cycle
(called
the
CPU
instruction
cycle).
The
CPU
instruction
cycle
designates
a
certain
number
of
repetitions,
and
this
is
the
number
of
times
the
basic
computing
instructions
will
be
repeated,
as
permitted
by
that
computer’s
processing
power.

The
basic
computing
instructions
include
the
following:

• 
  Fetch:
  Fetches
  occur
  anytime
  data
  is
  retrieved
  from
  memory.
• 
  Decode:
  The
  decoder
  within
  the
  CPU
  translates
  binary
  instructions
  into
  electrical
  signals
  that
  engage
  with
  other
  parts
  of
  the
  CPU.
• 
  Execute:
  Execution
  occurs
  when
  computers
  interpret
  and
  carry
  out
  a
  computer
  program’s
  set
  of
  instructions.

With
some
basic
tinkering,
the
computer
clock
within
a
CPU
can
be
manipulated
to
keep
time
faster
than
it
normally
elapses.
Some
users
do
this
to
run
their
computer
at
higher
speeds.
However,
this
practice
(“overclocking”)
is
not
advisable
since
it
can
cause
computer
parts
to
wear
out
earlier
than
normal
and
can
even
violate
CPU
manufacturer
warranties.

Processing
styles
are
also
subject
to
tweaking.
One
way
to
manipulate
those
is
by
implementing
instruction
pipelining,
which
seeks
to
instill
instruction-level
parallelism
in
a
single
processor.
The
goal
of
pipelining
is
to
keep
each
part
of
the
processor
engaged
by
splitting
up
incoming
computer
instructions
and
spreading
them
out
evenly
among
processor
units.
Instructions
are
broken
down
into
smaller
sets
of
instructions
or
steps.

Another
method
for
achieving
instruction-level
parallelism
inside
a
single
processor
is
to
use
a
CPU
called
a
superscalar
processor.
Whereas
scalar
processors
can
execute
a
maximum
of
one
instruction
per
clock
cycle,
there’s
really
no
limit
to
how
many
instructions
can
be
dispatched
by
a
superscalar
processor.
It
sends
multiple
instructions
to
various
of
the
processor’s
execution
units,
thereby
boosting
throughput.

Who
invented
the
CPU?

Breakthrough
technologies
often
have
more
than
one
parent.
The
more
complex
and
earth-shaking
that
technology,
the
more
individuals
who
are
usually
responsible
for
that
birth.

In
the
case
of
the
CPU—one
of
history’s
most
important
inventions—we’re
really
talking
about
who
discovered
the
computer
itself.

Anthropologists
use
the
term
“independent
invention”
to
describe
situations
where
different
individuals,
who
may
be
located
countries
away
from
each
other
and
in
relative
isolation,
each
come
up
with
what
are
similar
or
complementary
ideas
or
inventions
without
knowing
about
similar
experiments
taking
place.

In
the
case
of
the
CPU
(or
computer),
independent
invention
has
occurred
repeatedly,
leading
to
different
evolutionary
shifts
during
CPU
history.

Twin
giants
of
computing

While
this
article
can’t
honor
all
the
early
pioneers
of
computing,
there
are
two
people
whose
lives
and
work
need
to
be
illuminated.
Both
had
a
direct
connection
to
computing
and
the
CPU:

Grace
Hopper:
Saluting
“Grandma
COBOL”

American
Grace
Brewster
Hopper
(1906-1992)
weighed
a
mere
105
pounds
when
she
enlisted
in
the
US
Navy—15
pounds
under
the
required
weight
limit.
And
in
one
of
US
maritime
history’s
wisest
decisions,
the
Navy
gave
an
exemption
and
took
her
anyway.

What
Grace
Hopper
lacked
in
physical
size,
she
made
up
for
with
energy
and
versatile
brilliance.
She
was
a
polymath
of
the
first
order:
a
gifted
mathematician
armed
with
twin
Ph.D.
degrees
from
Yale
University
in
both
mathematics
and
mathematical
physics,
a
noted
professor
of
mathematics
at
Vassar
College,
a
pioneering
computer
scientist
credited
with
writing
a
computer
language
and
authoring
the
first
computer
manual,
and
a
naval
commander
(at
a
time
when
women
rarely
rose
above
administrative
roles
in
the
military).

Because
of
her
work
on
leading
computer
projects
of
her
time,
such
as
the
development
of
the
UNIVAC
supercomputer
after
WWII,
Hopper
always
seemed
in
the
thick
of
the
action,
always
at
the
right
place
at
the
right
time.
She
had
personally
witnessed
much
of
modern
computing
history.
She
was
the
person
who
originally
coined
the
term
“computer
bug,”
describing
an
actual
moth
that
had
become
caught
within
a
piece
of
computing
equipment.
(The
original
moth
remains
on
display
at
the
Smithsonian
Institution’s
National
Museum
of
American
History
in
Washington,
DC.)

During
her
experience
working
on
the
UNIVAC
project
(and
later
running
the
UNIVAC
project
for
the
Remington
Rand
Corporation),
Hopper
became
frustrated
that
there
was
not
a
simpler
programming
language
that
could
be
used.
So,
she
set
about
writing
her
own
programming
language,
which
famously
came
to
be
known
as
COBOL
(an
acronym
for

COmmon

Business-Oriented

Language).

Robert
Noyce:
The
Mayor
of
Silicon
Valley

Robert
Noyce
was
a
mover
and
shaker
in
the
classic
business
sense—a
person
who
could
make
amazing
activity
start
happening
just
by
showing
up.

American
Robert
Noyce
(1927-1990)
was
a
whiz-kid
boy
inventor.
He
later
channeled
his
intellectual
curiosity
into
his
undergrad
collegiate
work,
especially
after
being
shown
two
of
the
original
transistors
created
by
Bell
Laboratories.
By
age
26,
Noyce
earned
a
Ph.D.
in
Physics
from
the
Massachusetts
Institute
of
Technology
(MIT).

In
1959,
he
followed
up
on
Jack
Kilby’s
1958
invention
of
the
first
hybrid
integrated
circuit
by
making
substantial
tweaks
to
the
original
design.
Noyce’s
improvements
led
to
a
new
kind
of
integrated
circuits:
the
monolithic
integrated
circuit
(also
called
the
microchip),
which
was
formulated
using
silicon.
Soon
the
silicon
chip
became
a
revelation,
changing
industries
and
shaping
society
in
new
ways.

Noyce
co-founded
two
hugely
successful
corporations
during
his
business
career:
Fairchild
Semiconductor
Corporation
(1957)
and
Intel
(1968).
He
was
the
first
CEO
of
Intel,
which
is
still
known
globally
for
manufacturing
processing
chips.

His
partner
in
both
endeavors
was
Gordon
Moore,
who
became
famous
for
a
prediction
about
the
semiconductor
industry
that
proved
so
reliable
it
has
seemed
almost
like
an
algorithm.
Called
“Moore’s
Law,”
it
posited
that
the
number
of
transistors
to
be
used
within
an
integrated
circuit
reliably
doubles
about
every
two
years.

While
Noyce
oversaw
Intel,
the
company
produced
the
Intel
4004,
now
recognized
as
the
chip
that
launched
the
microprocessor
revolution
of
the
1970s.
The
creation
of
the
Intel
4004
involved
a
three-way
collaboration
between
Intel’s
Ted
Hoff,
Stanley
Mazor
and
Federico
Faggin,
and
it
became
the
first
microprocessor
ever
offered
commercially.

Late
in
his
tenure,
the
company
also
produced
the
Intel
8080—the
company’s
second
8-bit
microprocessor,
which
first
appeared
in
April
1974.
Within
a
couple
of
years
of
that,
the
manufacturer
was
rolling
out
the
Intel
8086,
a
16-bit
microprocessor.

During
his
illustrious
career,
Robert
Noyce
amassed
12
patents
for
various
creations
and
was
honored
by
three
different
US
presidents
for
his
work
on
integrated
circuits
and
the
massive
global
impact
they
had.

ENIAC:
Marching
off
to
war

It
seems
overly
dramatic,
but
in
1943,
the
fate
of
the
world
truly
was
hanging
in
the
balance.
The
outcome
of
World
War
II
(1939-1945)
was
still
very
much
undecided,
and
both
Allies
forces
and
Axis
forces
were
eagerly
scouting
any
kind
of
technological
advantage
to
gain
leverage
over
the
enemy.

Computer
devices
were
still
in
their
infancy
when
a
project
as
monumental
in
its
way
as
the
Manhattan
Project
was
created.
The
US
government
hired
a
group
of
engineers
from
the
Moore
School
of
Electrical
Engineering
at
the
University
of
Pennsylvania.
The
mission
called
upon
them
to
build
an
electronic
computer
capable
of
calculating
yardage
amounts
for
artillery-range
tables.

The
project
was
led
by
John
Mauchly
and
J.
Presper
Eckert,
Jr.
at
the
military’s
request.
Work
began
on
the
project
in
early
1943
and
didn’t
end
until
3
years
later.

The
creation
produced
by
the
project—dubbed
ENIAC,
which
stood
for
“Electronic
Numerical
Integrator
and
Computer”—was
a
massive
installation
requiring
1,500
sq.
ft.
of
floor
space,
not
to
mention
17,000
glass
vacuum
tubes,
70,000
resistors,
10,000
capacitors,
6,000
switches
and
1,500
relays.
In
2024
currency,
the
project
would
have
cost
USD
6.7
million.

It
could
process
up
to
5,000
equations
per
second
(depending
on
the
equation),
an
amazing
quantity
as
seen
from
that
historical
vantage
point.
Due
to
its
generous
size,
the
ENIAC
was
so
large
that
people
could
stand
within
the
CPU
and
program
the
machine
by
rewiring
connections
between
functional
units
in
the
machine.
 

ENIAC
was
used
by
the
US
Army
during
the
rest
of
WWII.
But
when
that
conflict
ended,
the
Cold
War
began
and
ENIAC
was
given
new
marching
orders.
This
time
it
would
perform
calculations
that
would
help
enable
the
building
of
a
bomb
with
more
than
a
thousand
times
the
explosive
force
of
the
atomic
weapons
that
ended
WWII:
the
hydrogen
bomb.

UNIVAC:
Getting
back
to
business

Following
WWII,
the
two
leaders
of
the
ENIAC
project
decided
to
set
up
shop
and
bring
computing
to
American
business.
The
newly
dubbed
Eckert-Mauchly
Computer
Corporation
(EMCC)
set
out
to
prepare
its
flagship
product—a
smaller
and
cheaper
version
of
the
ENIAC,
with
various
improvements
like
added
tape
drives,
a
keyboard
and
a
converter
device
that
accepted
punch-card
use.

Though
sleeker
than
the
ENIAC,
the
UNIVAC
that
was
unveiled
to
the
public
in
1951
was
still
mammoth,
weighing
over
8
tons
and
using
125
kW
of
energy.
And
it
was
still
expensive:
around
USD
11.6
million
in
today’s
money.

For
its
CPU,
it
contained
the
first
CPU—the
UNIVAC
1103—which
was
developed
at
the
same
time
as
the
rest
of
the
project.
The
UNIVAC
1103
used
glass
vacuum
tubes,
making
the
CPU
large,
unwieldy
and
slow.

The
original
batch
of
UNIVAC
1s
was
limited
to
a
run
of
11
machines,
meaning
that
only
the
biggest,
best-funded
and
best-connected
companies
or
government
agencies
could
gain
access
to
a
UNIVAC.
Nearly
half
of
those
were
US
defense
agencies,
like
the
US
Air
Force
and
the
Central
Intelligence
Agency
(CIA).
The
very
first
model
was
purchased
by
the
U.S.
Census
Bureau.

CBS
News
had
one
of
the
machines
and
famously
used
it
to
correctly
predict
the
outcome
of
the
1952
US
Presidential
election,
against
long-shot
odds.
It
was
a
bold
publicity
stunt
that
introduced
the
American
public
to
the
wonders
that
computers
could
do.

Transistors:
Going
big
by
going
small

As
computing
increasingly
became
realized
and
celebrated,
its
main
weakness
was
clear.
CPUs
had
an
ongoing
issue
with
the
vacuum
tubes
being
used.
It
was
really
a
mechanical
issue:
Glass
vacuum
tubes
were
extremely
delicate
and
prone
to
routine
breakage.

The
problem
was
so
pronounced
that
the
manufacturer
went
to
great
lengths
to
provide
a
workaround
solution
for
its
many
agitated
customers,
whose
computers
stopped
dead
without
working
tubes.

The
manufacturer
of
the
tubes
regularly
tested
tubes
at
the
factory,
subjecting
tubes
to
different
amounts
of
factory
use
and
abuse,
before
selecting
the
“toughest”
tubes
out
of
those
batches
to
be
held
in
reserve
and
at
the
ready
for
emergency
customer
requests.

The
other
problem
with
the
vacuum
tubes
in
CPUs
involved
the
size
of
the
computing
machine
itself.
The
tubes
were
bulky
and
designers
were
craving
a
way
to
get
the
processing
power
of
the
tube
from
a
much
smaller
device.

By
1953,
a
research
student
at
the
University
of
Manchester
showed
you
could
construct
a
completely

transistor-based
computer.

Original
transistors
were
hard
to
work
with,
in
large
part
because
they
were
crafted
from
germanium,
a
substance
which
was
tricky
to
purify
and
had
to
be
kept
within
a
precise
temperature
range.

Bell
Laboratory
scientists
started
experimenting
with
other
substances
in
1954,
including
silicon.
The
Bell
scientists
(Mohamed
Italia
and
Dawn
Kahng)
kept
refining
their
use
of
silicon
and
by
1960
had
hit
upon
a
formula
for
the
metal-oxide-semiconductor
field-effect
transistor
(or
MOSFET,
or
MOS
transistor)
modern
transistor,
which
has
been
celebrated
as
the
“most
widely
manufactured
device
in
history,”
by
the
Computer
History
Museum.
In
2018
it
was
estimated
that

13
sextillion
MOS
transistors
had
been
manufactured.

The
advent
of
the
microprocessor

The
quest
for
miniaturization
continued
until
computer
scientists
created
a
CPU
so
small
that
it
could
be
contained
within
a
small
integrated
circuit
chip,
called
the
microprocessor.

Microprocessors
are
designated
by
the
number
of
cores
they
support.
A
CPU
core
is
the
“brain
within
the
brain,”
serving
as
the
physical
processing
unit
within
a
CPU.
Microprocessors
can
contain
multiple
processors.
Meanwhile,
a
physical
core
is
a
CPU
built
into
a
chip,
but
which
only
occupies
one
socket,
thus
enabling
other
physical
cores
to
tap
into
the
same
computing
environment.

Here
are
some
of
the
other
main
terms
used
in
relation
to
microprocessors:

• 
  Single-core
  processors:
  Single-core
  processors
  contain
  a
  single
  processing
  unit.
  They
  are
  typically
  marked
  by
  slower
  performance,
  run
  on
  a
  single
  thread
  and
  perform
  the
  CPU
  instruction
  cycle
  one
  at
  a
  time.
• 
  Dual-core
  processors:
  Dual-core
  processors
  are
  equipped
  with
  two
  processing
  units
  contained
  within
  one
  integrated
  circuit.
  Both
  cores
  run
  at
  the
  same
  time,
  effectively
  doubling
  performance
  rates.
• 
  Quad-core
  processors:
  Quad-core
  processors
  contain
  four
  processing
  units
  within
  a
  single
  integrated
  circuit.
  All
  cores
  run
  simultaneously,
  quadrupling
  performance
  rates.
• 
  Multi-core
  processors:
  Multi-core
  processors
  are
  integrated
  circuits
  equipped
  with
  at
  least
  two
  processor
  cores,
  so
  they
  can
  deliver
  supreme
  performance
  and
  optimized
  power
  consumption.

Leading
CPU
manufacturers

Several
companies
now
create
products
that
support
CPUs
through
different
brand
lines.
However,
this
market
niche
has
changed
dramatically,
given
that
it
formerly
attracted
numerous
players,
including
plenty
of
mainstream
manufacturers
(e.g.,
Motorola).
Now
there’s
really
just
a
couple
of
main
players:
Intel
and
AMD.

They
use
differing
instruction
set
architectures
(ISAs).
So,
while
AMD
processors
take
their
cues
from
Reduced
Instruction
Set
Computer
(RISC)
architecture,
Intel
processors
follow
a
Complex
Instruction
Set
Computer
(CISC)
architecture.

• 
  Advanced
  Micro
  Devices
  (AMD):
  AMD
  sells
  processors
  and
  microprocessors
  through
  two
  product
  types:
  CPUs
  and
  APUs
  (which
  stands
  for
  accelerated
  processing
  units).
  In
  this
  case,
  APUs
  are
  simply
  CPUs
  that
  have
  been
  equipped
  with
  proprietary
  Radeon
  graphics.
  AMD’s
  Ryzen
  processors
  are
  high-speed,
  high-performance
  microprocessors
  intended
  for
  the
  video-game
  market.
  Athlon
  processors
  was
  formerly
  considered
  AMD’s
  high-end
  line,
  but
  AMD
  now
  uses
  it
  as
  a
  general-purpose
  alternative.
• 
  Arm:
  Arm
  doesn’t
  actually
  manufacture
  equipment,
  but
  does
  lease
  out
  its
  valued
  processor
  designs
  and/or
  other
  proprietary
  technologies
  to
  other
  companies
  who
  make
  equipment.
  Apple,
  for
  example,
  no
  longer
  uses
  Intel
  chips
  in
  Mac
  CPUs,
  but
  makes
  its
  own
  customized
  processors
  based
  on
  Arm
  designs.
  Other
  companies
  are
  following
  suit.
• 
  Intel:
  Intel
  sells
  processors
  and
  microprocessors
  through
  four
  product
  lines.
  Its
  premium
  line
  is
  Intel
  Core,
  including
  processor
  models
  like
  the
  Core
  i3.
  Intel’s
  Xeon
  processors
  are
  marketed
  toward
  offices
  and
  businesses.
  Intel’s
  Celeron
  and
  Intel
  Pentium
  lines
  (represented
  by
  models
  like
  the
  Pentium
  4
  single-core
  CPUs)
  are
  considered
  slower
  and
  less
  powerful
  than
  the
  Core
  line.

Understanding
the
dependable
role
of
CPUs

When
considering
CPUs,
we
can
think
about
the
various
components
that
CPUs
contain
and
use.
We
can
also
contemplate
how
CPU
design
has
moved
from
its
early
super-sized
experiments
to
its
modern
period
of
miniaturization.

But
despite
any
transformations
to
its
dimensions
or
appearance,
the
CPU
remains
steadfastly
itself,
still
on
the
job—because
it’s
so
good
at
its
particular
job.
You
know
you
can
trust
it
to
work
correctly,
each
time
out.

Smart
computing
depends
upon
having
proper
equipment
you
can
rely
upon.
IBM
builds
its
servers
strong,
to
withstand
any
problems
the
modern
workplace
can
throw
at
them.
Find
the
IBM
servers
you
need
to
get
the
results
your
organization
relies
upon.

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