<s>
Whirlwind	B-Device
I	I-Device
was	O
a	O
Cold	O
War-era	O
vacuum	B-Architecture
tube	I-Architecture
computer	I-Architecture
developed	O
by	O
the	O
MIT	O
Servomechanisms	O
Laboratory	O
for	O
the	O
U.S.	O
Navy	O
.	O
</s>
<s>
It	O
was	O
one	O
of	O
the	O
first	B-Architecture
computers	I-Architecture
to	O
calculate	O
in	O
parallel	B-Operating_System
(	O
rather	O
than	O
serial	B-Device
)	O
,	O
and	O
was	O
the	O
first	O
to	O
use	O
magnetic-core	O
memory	O
.	O
</s>
<s>
Its	O
development	O
led	O
directly	O
to	O
the	O
Whirlwind	B-Device
II	I-Device
design	O
used	O
as	O
the	O
basis	O
for	O
the	O
United	O
States	O
Air	O
Force	O
SAGE	B-Device
air	I-Device
defense	I-Device
system	I-Device
,	O
and	O
indirectly	O
to	O
almost	O
all	O
business	O
computers	O
and	O
minicomputers	B-Architecture
in	O
the	O
1960s	O
,	O
particularly	O
because	O
of	O
the	O
mantra	O
"	O
short	O
word	O
length	O
,	O
speed	O
,	O
people.	O
"	O
</s>
<s>
During	O
World	O
War	O
II	O
,	O
the	O
U.S.	O
Navy	O
's	O
Naval	O
Research	O
Lab	O
approached	O
MIT	O
about	O
the	O
possibility	O
of	O
creating	O
a	O
computer	O
to	O
drive	O
a	O
flight	B-Application
simulator	I-Application
for	O
training	O
bomber	B-Application
crews	O
.	O
</s>
<s>
The	O
Navy	O
's	O
Office	O
of	O
Naval	O
Research	O
decided	O
to	O
fund	O
development	O
under	O
Project	B-Device
Whirlwind	I-Device
(	O
and	O
its	O
sister	O
projects	O
,	O
Project	O
Typhoon	O
and	O
Project	O
Cyclone	O
,	O
with	O
other	O
institutions	O
)	O
,	O
and	O
the	O
lab	O
placed	O
Jay	O
Forrester	O
in	O
charge	O
of	O
the	O
project	O
.	O
</s>
<s>
Perry	O
Crawford	O
,	O
another	O
member	O
of	O
the	O
MIT	O
team	O
,	O
saw	O
a	O
demonstration	O
of	O
ENIAC	B-Device
in	O
1945	O
.	O
</s>
<s>
Such	O
a	O
machine	O
would	O
allow	O
the	O
accuracy	O
of	O
simulations	O
to	O
be	O
improved	O
with	O
the	O
addition	O
of	O
more	O
code	O
in	O
the	O
computer	B-Application
program	I-Application
,	O
as	O
opposed	O
to	O
adding	O
parts	O
to	O
the	O
machine	O
.	O
</s>
<s>
Until	O
this	O
point	O
,	O
all	O
computers	O
constructed	O
were	O
dedicated	O
to	O
single	O
tasks	O
,	O
and	O
run	O
in	O
batch	B-General_Concept
mode	I-General_Concept
.	O
</s>
<s>
This	O
was	O
not	O
appropriate	O
for	O
the	O
Whirlwind	B-Device
system	O
,	O
which	O
needed	O
to	O
operate	O
continually	O
on	O
an	O
ever-changing	O
series	O
of	O
inputs	O
.	O
</s>
<s>
Speed	O
became	O
a	O
major	O
issue	O
:	O
whereas	O
with	O
other	O
systems	O
it	O
simply	O
meant	O
waiting	O
longer	O
for	O
the	O
printout	O
,	O
with	O
Whirlwind	B-Device
it	O
meant	O
seriously	O
limiting	O
the	O
amount	O
of	O
complexity	O
the	O
simulation	O
could	O
include	O
.	O
</s>
<s>
Most	O
computers	O
of	O
the	O
era	O
operated	O
in	O
bit-serial	O
mode	O
,	O
using	O
single-bit	O
arithmetic	O
and	O
feeding	O
in	O
large	O
words	O
,	O
often	O
48	O
or	O
60	O
bits	O
in	O
size	O
,	O
one	O
bit	O
at	O
a	O
time	O
.	O
</s>
<s>
This	O
was	O
simply	O
not	O
fast	O
enough	O
for	O
their	O
purposes	O
,	O
so	O
Whirlwind	B-Device
included	O
sixteen	O
such	O
math	O
units	O
,	O
operating	O
on	O
a	O
complete	O
16-bit	O
word	O
every	O
cycle	O
in	O
bit-parallel	O
mode	O
.	O
</s>
<s>
Ignoring	O
memory	O
speed	O
,	O
Whirlwind	B-Device
(	O
"	O
20,000	O
single-address	O
operations	O
per	O
second	O
"	O
in	O
1951	O
)	O
was	O
essentially	O
sixteen	O
times	O
as	O
fast	O
as	O
other	O
machines	O
.	O
</s>
<s>
Today	O
,	O
almost	O
all	O
CPUs	O
perform	O
arithmetic	O
in	O
"	O
bit-parallel	O
"	O
mode	O
.	O
</s>
<s>
Whirlwind	B-Device
operated	O
much	O
like	O
a	O
reverse	O
Polish	O
notation	O
calculator	B-Application
in	O
this	O
respect	O
;	O
except	O
there	O
was	O
no	O
operand	O
stack	O
,	O
only	O
an	O
accumulator	B-General_Concept
.	O
</s>
<s>
The	O
Whirlwind	B-Device
design	O
incorporated	O
a	O
control	B-General_Concept
store	I-General_Concept
driven	O
by	O
a	O
master	O
clock	O
.	O
</s>
<s>
Each	O
step	O
of	O
the	O
clock	O
selected	O
one	O
or	O
more	O
signal	O
lines	O
in	O
a	O
diode	B-General_Concept
matrix	I-General_Concept
that	O
enabled	O
gates	O
and	O
other	O
circuits	O
on	O
the	O
machine	O
.	O
</s>
<s>
In	O
the	O
early	O
1950s	O
,	O
Whirlwind	B-Device
I	I-Device
"	O
would	O
crash	O
every	O
20	O
minutes	O
on	O
average.	O
"	O
</s>
<s>
Whirlwind	B-Device
construction	O
started	O
in	O
1948	O
,	O
an	O
effort	O
that	O
employed	O
175	O
people	O
,	O
including	O
70	O
engineers	O
and	O
technicians	O
.	O
</s>
<s>
Finally	O
Whirlwind	B-Device
"	O
successfully	O
accomplished	O
digital	O
computation	O
of	O
interception	O
courses	O
"	O
on	O
April	O
20	O
,	O
1951	O
.	O
</s>
<s>
However	O
,	O
during	O
this	O
time	O
the	O
Air	O
Force	O
had	O
become	O
interested	O
in	O
using	O
computers	O
to	O
help	O
the	O
task	O
of	O
ground	B-Device
controlled	I-Device
interception	I-Device
,	O
and	O
the	O
Whirlwind	B-Device
was	O
the	O
only	O
machine	O
suitable	O
to	O
the	O
task	O
.	O
</s>
<s>
Whirlwind	B-Device
weighed	O
.	O
</s>
<s>
The	O
only	O
two	O
available	O
memory	O
technologies	O
in	O
1949	O
that	O
could	O
hold	O
this	O
much	O
data	O
were	O
mercury	O
delay	O
lines	O
and	O
electrostatic	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
The	O
Whirlwind	B-Device
designers	O
quickly	O
discarded	O
the	O
delay	O
line	O
as	O
a	O
possible	O
memory	O
—	O
it	O
was	O
both	O
too	O
slow	O
for	O
the	O
envisioned	O
flight	B-Application
simulator	I-Application
,	O
and	O
too	O
unreliable	O
for	O
a	O
reproducible	O
production	O
system	O
,	O
for	O
which	O
Whirlwind	B-Device
was	O
intended	O
to	O
be	O
a	O
functional	O
prototype	O
.	O
</s>
<s>
This	O
was	O
a	O
cathode	B-Device
ray	I-Device
tube	I-Device
memory	O
,	O
similar	O
in	O
many	O
aspects	O
to	O
an	O
early	O
TV	O
picture	B-Device
tube	I-Device
or	O
oscilloscope	O
tube	O
.	O
</s>
<s>
The	O
best	O
known	O
today	O
is	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
,	O
developed	O
in	O
England	O
,	O
but	O
there	O
were	O
a	O
number	O
of	O
others	O
that	O
had	O
been	O
developed	O
independently	O
by	O
various	O
research	O
labs	O
.	O
</s>
<s>
The	O
Whirlwind	B-Device
engineers	O
considered	O
the	O
Williams	B-General_Concept
tube	I-General_Concept
,	O
but	O
determined	O
that	O
the	O
dynamic	O
nature	O
of	O
the	O
storage	O
and	O
the	O
need	O
for	O
frequent	O
refresh	B-General_Concept
cycles	I-General_Concept
was	O
incompatible	O
with	O
the	O
design	O
goals	O
for	O
Whirlwind	B-Device
I	I-Device
.	O
</s>
<s>
As	O
a	O
result	O
of	O
the	O
design	O
,	O
this	O
tube	O
was	O
more	O
of	O
a	O
static	B-Architecture
RAM	I-Architecture
that	O
did	O
not	O
require	O
refresh	B-General_Concept
cycles	I-General_Concept
,	O
unlike	O
the	O
dynamic	O
RAM	O
Williams	B-General_Concept
tube	I-General_Concept
.	O
</s>
<s>
The	O
Williams	B-General_Concept
tube	I-General_Concept
was	O
considerably	O
better	O
developed	O
,	O
and	O
despite	O
the	O
need	O
for	O
refresh	O
could	O
easily	O
hold	O
1024bits	O
per	O
tube	O
,	O
and	O
was	O
quite	O
reliable	O
when	O
operated	O
correctly	O
.	O
</s>
<s>
Also	O
,	O
the	O
specifications	O
had	O
called	O
for	O
an	O
access	B-General_Concept
time	I-General_Concept
of	O
six	O
microseconds	O
,	O
but	O
the	O
actual	O
access	B-General_Concept
time	I-General_Concept
was	O
around	O
30microseconds	O
.	O
</s>
<s>
Since	O
the	O
basic	O
cycle	O
time	O
of	O
the	O
WhirlwindI	O
processor	O
was	O
determined	O
by	O
the	O
memory	O
access	B-General_Concept
time	I-General_Concept
,	O
the	O
entire	O
processor	O
was	O
slower	O
than	O
designed	O
.	O
</s>
<s>
Initially	O
the	O
computer	O
only	O
had	O
32	O
words	O
of	O
storage	O
,	O
and	O
27	O
of	O
these	O
words	O
were	O
read-only	B-Device
registers	O
made	O
of	O
toggle	O
switches	O
.	O
</s>
<s>
The	O
remaining	O
five	O
registers	O
were	O
flip-flop	B-General_Concept
storage	O
,	O
with	O
each	O
of	O
the	O
five	O
registers	O
being	O
made	O
from	O
more	O
than	O
30	O
vacuum	O
tubes	O
.	O
</s>
<s>
The	O
main	O
memory	O
was	O
so	O
late	O
that	O
the	O
first	O
experiments	O
of	O
tracking	O
airplanes	O
with	O
live	O
radar	B-Application
data	O
were	O
done	O
using	O
a	O
program	O
manually	O
set	O
into	O
test	O
storage	O
.	O
</s>
<s>
(	O
Buck	O
would	O
go	O
on	O
to	O
invent	O
the	O
cryotron	O
and	O
content-addressable	B-Data_Structure
memory	I-Data_Structure
at	O
the	O
lab	O
.	O
)	O
</s>
<s>
The	O
large	O
number	O
of	O
tubes	O
used	O
in	O
Whirlwind	B-Device
resulted	O
in	O
a	O
problematic	O
failure	O
rate	O
since	O
a	O
single	O
tube	O
failure	O
could	O
cause	O
a	O
system	O
failure	O
.	O
</s>
<s>
The	O
7AK7	B-Device
tube	O
with	O
a	O
high-purity	O
tungsten	O
filament	O
was	O
then	O
specially	O
developed	O
for	O
Whirlwind	B-Device
by	O
Sylvania	O
.	O
</s>
<s>
Of	O
the	O
1,412	O
7AK7	B-Device
tubes	O
in	O
use	O
,	O
18	O
failed	O
,	O
of	O
which	O
only	O
2	O
failed	O
during	O
marginal	O
checking	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
Whirlwind	B-Device
was	O
far	O
more	O
reliable	O
than	O
any	O
commercially	O
available	O
machine	O
.	O
</s>
<s>
Many	O
other	O
features	O
of	O
the	O
Whirlwind	B-Device
tube	O
testing	O
regime	O
were	O
not	O
standard	O
tests	O
and	O
required	O
specially	O
built	O
equipment	O
.	O
</s>
<s>
After	O
connection	O
to	O
the	O
experimental	O
Microwave	O
Early	O
Warning	O
(	O
MEW	O
)	O
radar	B-Application
at	O
Hanscom	O
Field	O
using	O
Jack	O
Harrington	O
's	O
equipment	O
and	O
commercial	O
phone	O
lines	O
,	O
aircraft	O
were	O
tracked	O
by	O
Whirlwind	B-Device
I	I-Device
.	O
</s>
<s>
Signals	O
from	O
three	O
long	O
range	O
(	O
AN/FPS	O
-3	O
)	O
radars	B-Application
,	O
eleven	O
gap-filler	O
radars	B-Application
,	O
and	O
three	O
height-finding	O
radars	B-Application
were	O
transmitted	O
over	O
telephone	O
lines	O
to	O
the	O
Whirlwind	B-Device
I	I-Device
computer	O
in	O
Cambridge	O
,	O
Massachusetts	O
.	O
</s>
<s>
The	O
Whirlwind	B-Device
II	I-Device
design	O
for	O
a	O
larger	O
and	O
faster	O
machine	O
(	O
never	O
completed	O
)	O
was	O
the	O
basis	O
for	O
the	O
SAGE	B-Device
air	I-Device
defense	I-Device
system	I-Device
IBM	B-Device
AN/FSQ	I-Device
-7	I-Device
Combat	I-Device
Direction	I-Device
Central	I-Device
.	O
</s>
<s>
The	O
Whirlwind	B-Device
used	O
approximately	O
5,000	O
vacuum	O
tubes	O
.	O
</s>
<s>
An	O
effort	O
was	O
also	O
started	O
to	O
convert	O
the	O
Whirlwind	B-Device
design	O
to	O
a	O
transistorized	O
form	O
,	O
led	O
by	O
Ken	O
Olsen	O
and	O
known	O
as	O
the	O
TX-0	B-Device
.	O
</s>
<s>
TX-0	B-Device
was	O
very	O
successful	O
and	O
plans	O
were	O
made	O
to	O
make	O
an	O
even	O
larger	O
version	O
known	O
as	O
TX-1	O
.	O
</s>
<s>
However	O
this	O
project	O
was	O
far	O
too	O
ambitious	O
and	O
had	O
to	O
be	O
scaled	O
back	O
to	O
a	O
smaller	O
version	O
known	O
as	O
TX-2	B-Device
.	O
</s>
<s>
DEC	O
's	O
PDP-1	B-Device
was	O
essentially	O
a	O
collection	O
of	O
TX-0	B-Device
and	O
TX-2	B-Device
concepts	O
in	O
a	O
smaller	O
package	O
.	O
</s>
<s>
After	O
supporting	O
SAGE	B-Device
,	O
Whirlwind	B-Device
I	I-Device
was	O
rented	O
( $	O
1/yr	O
)	O
from	O
June	O
30	O
,	O
1959	O
,	O
until	O
1974	O
by	O
project	O
member	O
,	O
Bill	O
Wolf	O
.	O
</s>
<s>
It	O
is	O
now	O
in	O
the	O
collection	O
of	O
the	O
Computer	B-Architecture
History	I-Architecture
Museum	O
in	O
Mountain	O
View	O
,	O
California	O
.	O
</s>
<s>
One	O
plane	O
of	O
core	O
memory	O
,	O
on	O
loan	O
from	O
the	O
Computer	B-Architecture
History	I-Architecture
Museum	O
,	O
is	O
on	O
shown	O
as	O
part	O
of	O
the	O
Historic	O
Computer	O
Science	O
displays	O
at	O
the	O
Gates	O
Computer	O
Science	O
Building	O
,	O
Stanford	O
.	O
</s>
<s>
The	O
building	O
which	O
housed	O
Whirlwind	B-Device
was	O
until	O
recently	O
home	O
to	O
MIT	O
's	O
campus-wide	O
IT	O
department	O
,	O
Information	O
Services	O
&	O
Technology	O
and	O
in	O
1997	O
–	O
1998	O
,	O
it	O
was	O
restored	O
to	O
its	O
original	O
exterior	O
design	O
.	O
</s>
