<s>
Bubble	B-General_Concept
memory	I-General_Concept
is	O
a	O
type	O
of	O
non-volatile	B-General_Concept
computer	B-General_Concept
memory	I-General_Concept
that	O
uses	O
a	O
thin	O
film	O
of	O
a	O
magnetic	O
material	O
to	O
hold	O
small	O
magnetized	O
areas	O
,	O
known	O
as	O
bubbles	O
or	O
domains	O
,	O
each	O
storing	O
one	O
bit	O
of	O
data	O
.	O
</s>
<s>
In	O
operation	O
,	O
bubble	B-General_Concept
memories	I-General_Concept
are	O
similar	O
to	O
delay-line	O
memory	O
systems	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
started	O
out	O
as	O
a	O
promising	O
technology	O
in	O
the	O
1970s	O
,	O
offering	O
memory	B-Device
density	I-Device
of	O
an	O
order	O
similar	O
to	O
hard	B-Device
drives	I-Device
,	O
but	O
performance	O
more	O
comparable	O
to	O
core	B-General_Concept
memory	I-General_Concept
,	O
while	O
lacking	O
any	O
moving	O
parts	O
.	O
</s>
<s>
The	O
introduction	O
of	O
dramatically	O
faster	O
semiconductor	B-Architecture
memory	I-Architecture
chips	O
pushed	O
bubble	O
into	O
the	O
slow	O
end	O
of	O
the	O
scale	O
,	O
and	O
equally	O
dramatic	O
improvements	O
in	O
hard-drive	B-Device
capacity	O
made	O
it	O
uncompetitive	O
in	O
price	O
terms	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
was	O
used	O
for	O
some	O
time	O
in	O
the	O
1970s	O
and	O
1980s	O
where	O
its	O
non-moving	O
nature	O
was	O
desirable	O
for	O
maintenance	O
or	O
shock-proofing	O
reasons	O
.	O
</s>
<s>
The	O
introduction	O
of	O
flash	B-Device
storage	I-Device
and	O
similar	O
technologies	O
rendered	O
even	O
this	O
niche	O
uncompetitive	O
,	O
and	O
bubble	O
disappeared	O
entirely	O
by	O
the	O
late	O
1980s	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
is	O
largely	O
the	O
brainchild	O
of	O
a	O
single	O
person	O
,	O
Andrew	O
Bobeck	O
.	O
</s>
<s>
Bobeck	O
had	O
worked	O
on	O
many	O
kinds	O
of	O
magnetics-related	O
projects	O
through	O
the	O
1960s	O
,	O
and	O
two	O
of	O
his	O
projects	O
put	O
him	O
in	O
a	O
particularly	O
good	O
position	O
for	O
the	O
development	O
of	O
bubble	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
first	O
was	O
the	O
development	O
of	O
the	O
first	O
magnetic-core	O
memory	O
system	O
driven	O
by	O
a	O
transistor-based	O
controller	O
,	O
and	O
the	O
second	O
was	O
the	O
development	O
of	O
twistor	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Twistor	B-General_Concept
is	O
essentially	O
a	O
version	O
of	O
core	B-General_Concept
memory	I-General_Concept
that	O
replaces	O
the	O
"	O
cores	O
"	O
with	O
a	O
piece	O
of	O
magnetic	O
tape	O
.	O
</s>
<s>
The	O
main	O
advantage	O
of	O
twistor	B-General_Concept
is	O
its	O
ability	O
to	O
be	O
assembled	O
by	O
automated	O
machines	O
,	O
as	O
opposed	O
to	O
core	O
,	O
which	O
was	O
almost	O
entirely	O
manual	O
.	O
</s>
<s>
AT&T	O
had	O
great	O
hopes	O
for	O
twistor	B-General_Concept
,	O
believing	O
that	O
it	O
would	O
greatly	O
reduce	O
the	O
cost	O
of	O
computer	B-General_Concept
memory	I-General_Concept
and	O
put	O
them	O
in	O
an	O
industry	O
leading	O
position	O
.	O
</s>
<s>
Instead	O
,	O
DRAM	O
memories	O
came	O
onto	O
the	O
market	O
in	O
the	O
early	O
1970s	O
and	O
rapidly	O
replaced	O
all	O
previous	O
random-access	B-Architecture
memory	I-Architecture
systems	O
.	O
</s>
<s>
Twistor	B-General_Concept
ended	O
up	O
being	O
used	O
only	O
in	O
a	O
few	O
applications	O
,	O
many	O
of	O
them	O
T	O
's	O
own	O
computers	O
.	O
</s>
<s>
One	O
interesting	O
side	O
effect	O
of	O
the	O
twistor	B-General_Concept
concept	O
was	O
noticed	O
in	O
production	O
:	O
under	O
certain	O
conditions	O
,	O
passing	O
a	O
current	O
through	O
one	O
of	O
the	O
electrical	O
wires	O
running	O
inside	O
the	O
tape	O
would	O
cause	O
the	O
magnetic	O
fields	O
on	O
the	O
tape	O
to	O
move	O
in	O
the	O
direction	O
of	O
the	O
current	O
.	O
</s>
<s>
However	O
,	O
such	O
a	O
system	O
had	O
few	O
advantages	O
over	O
twistor	B-General_Concept
,	O
especially	O
as	O
it	O
did	O
not	O
allow	O
random	O
access	O
.	O
</s>
<s>
In	O
1967	O
,	O
Bobeck	O
joined	O
a	O
team	O
at	O
Bell	O
Labs	O
and	O
started	O
work	O
on	O
improving	O
twistor	B-General_Concept
.	O
</s>
<s>
The	O
memory	B-Device
density	I-Device
of	O
twistor	B-General_Concept
was	O
a	O
function	O
of	O
the	O
size	O
of	O
the	O
wires	O
;	O
the	O
length	O
of	O
any	O
one	O
wire	O
determined	O
how	O
many	O
bits	O
it	O
held	O
,	O
and	O
many	O
such	O
wires	O
were	O
laid	O
side-by-side	O
to	O
produce	O
a	O
larger	O
memory	O
system	O
.	O
</s>
<s>
Conventional	O
magnetic	O
materials	O
,	O
like	O
the	O
magnetic	O
tape	O
used	O
in	O
twistor	B-General_Concept
,	O
allowed	O
the	O
magnetic	O
signal	O
to	O
be	O
placed	O
at	O
any	O
location	O
and	O
to	O
move	O
in	O
any	O
direction	O
.	O
</s>
<s>
The	O
memory	B-General_Concept
device	I-General_Concept
and	O
method	O
of	O
propagation	O
were	O
described	O
in	O
a	O
paper	O
presented	O
at	O
the	O
13th	O
Annual	O
Conference	O
on	O
Magnetism	O
and	O
Magnetic	O
Materials	O
,	O
Boston	O
,	O
Massachusetts	O
,	O
15	O
September	O
1967	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
possibility	O
of	O
making	O
a	O
memory	O
system	O
similar	O
to	O
the	O
moving-domain	O
twistor	B-General_Concept
concept	O
,	O
but	O
using	O
a	O
single	O
block	O
of	O
magnetic	O
material	O
instead	O
of	O
many	O
twistor	B-General_Concept
wires	O
.	O
</s>
<s>
With	O
the	O
magnetic	O
tape	O
materials	O
used	O
in	O
twistor	B-General_Concept
,	O
the	O
data	O
had	O
to	O
be	O
stored	O
on	O
relatively	O
large	O
patches	O
known	O
as	O
domains	O
.	O
</s>
<s>
The	O
bubble	B-Application
system	I-Application
cannot	O
be	O
described	O
by	O
any	O
single	O
invention	O
,	O
but	O
in	O
terms	O
of	O
the	O
above	O
discoveries	O
.	O
</s>
<s>
The	O
next	O
problem	O
was	O
to	O
make	O
them	O
move	O
to	O
the	O
proper	O
location	O
where	O
they	O
could	O
be	O
read	O
back	O
out	O
:	O
twistor	B-General_Concept
was	O
a	O
wire	O
and	O
there	O
was	O
only	O
one	O
place	O
to	O
go	O
,	O
but	O
in	O
a	O
2D	O
sheet	O
things	O
would	O
not	O
be	O
so	O
easy	O
.	O
</s>
<s>
T	O
bars/guides	O
,	O
shaped	O
like	O
the	O
letters	O
,	O
were	O
used	O
in	O
early	O
bubble	B-General_Concept
memory	I-General_Concept
designs	O
,	O
but	O
were	O
later	O
replaced	O
by	O
other	O
shapes	O
such	O
as	O
asymmetrical	O
chevrons	O
.	O
</s>
<s>
Amorphous	O
magnetic	O
films	O
were	O
also	O
considered	O
as	O
they	O
had	O
greater	O
potential	O
for	O
improvement	O
of	O
bubble	B-General_Concept
memories	I-General_Concept
vs	O
garnet	O
magnetic	O
films	O
,	O
however	O
the	O
existing	O
experience	O
with	O
garnet	O
films	O
meant	O
that	O
they	O
did	O
not	O
gain	O
a	O
foothold	O
.	O
</s>
<s>
A	O
memory	B-General_Concept
device	I-General_Concept
is	O
formed	O
by	O
lining	O
up	O
tiny	O
electromagnets	O
at	O
one	O
end	O
with	O
detectors	O
at	O
the	O
other	O
end	O
.	O
</s>
<s>
Bubbles	O
written	O
in	O
would	O
be	O
slowly	O
pushed	O
to	O
the	O
other	O
,	O
forming	O
a	O
sheet	O
of	O
twistors	B-General_Concept
lined	O
up	O
beside	O
each	O
other	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
is	O
a	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Even	O
when	O
power	O
was	O
removed	O
,	O
the	O
bubbles	O
remained	O
,	O
just	O
as	O
the	O
patterns	O
do	O
on	O
the	O
surface	O
of	O
a	O
disk	B-Device
drive	I-Device
.	O
</s>
<s>
Better	O
yet	O
,	O
bubble	B-General_Concept
memory	I-General_Concept
devices	O
needed	O
no	O
moving	O
parts	O
:	O
the	O
field	O
that	O
pushed	O
the	O
bubbles	O
along	O
the	O
surface	O
was	O
generated	O
electrically	O
,	O
whereas	O
media	O
like	O
tape	O
and	O
disk	B-Device
drives	I-Device
required	O
mechanical	O
movement	O
.	O
</s>
<s>
A	O
bubble	B-General_Concept
memory	I-General_Concept
device	O
consists	O
of	O
a	O
case	O
,	O
that	O
houses	O
a	O
PCB	O
with	O
connections	O
to	O
one	O
or	O
more	O
bubble	B-General_Concept
memory	I-General_Concept
chips	O
,	O
which	O
may	O
be	O
translucent	O
.	O
</s>
<s>
The	O
permanent	O
magnets	O
are	O
critical	O
;	O
they	O
create	O
a	O
static	O
(	O
DC	O
,	O
direct	O
current	O
)	O
magnetic	O
field	O
,	O
used	O
as	O
a	O
bias	O
field	O
that	O
enables	O
the	O
contents	O
of	O
the	O
memory	O
to	O
be	O
retained	O
,	O
in	O
other	O
words	O
they	O
allow	O
bubble	B-General_Concept
memories	I-General_Concept
to	O
be	O
non-volatile	B-General_Concept
.	O
</s>
<s>
The	O
windings	O
create	O
a	O
rotating	O
magnetic	O
field	O
parallel	O
to	O
the	O
orientation	O
of	O
the	O
bubble	B-General_Concept
memory	I-General_Concept
,	O
at	O
around	O
100	O
to	O
200	O
khz	O
.	O
</s>
<s>
For	O
bubble	B-General_Concept
memory	I-General_Concept
,	O
a	O
material	O
like	O
Gadolinium	O
Gallium	O
Garnet	O
is	O
used	O
as	O
the	O
substrate	O
in	O
the	O
chips	O
.	O
</s>
<s>
The	O
materials	O
in	O
bubble	B-General_Concept
memories	I-General_Concept
are	O
chosen	O
mainly	O
for	O
their	O
magnetic	O
properties	O
.	O
</s>
<s>
Gadolinium	O
Gallium	O
Garnet	O
is	O
used	O
as	O
a	O
substrate	O
because	O
it	O
can	O
support	O
the	O
epitaxial	O
growth	O
of	O
magnetic	O
garnet	O
films	O
,	O
and	O
is	O
nonmagnetic	O
,	O
although	O
some	O
bubble	B-General_Concept
memories	I-General_Concept
used	O
Nickel-Cobalt	O
substrates	O
instead	O
.	O
</s>
<s>
The	O
use	O
of	O
propagation	O
elements	O
formed	O
by	O
ion	O
implantation	O
instead	O
of	O
permalloy	O
,	O
was	O
proposed	O
to	O
increase	O
the	O
capacity	O
of	O
bubble	B-General_Concept
memory	I-General_Concept
to	O
16	O
Mbit/cm2	O
.	O
</s>
<s>
Bobeck	O
's	O
team	O
soon	O
had	O
square	O
memories	O
that	O
stored	O
4,096	O
bits	O
,	O
the	O
same	O
as	O
a	O
then-standard	O
plane	O
of	O
core	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Not	O
only	O
could	O
bubble	B-General_Concept
memories	I-General_Concept
replace	O
core	O
but	O
it	O
seemed	O
that	O
they	O
could	O
replace	O
tapes	O
and	O
disks	B-Device
as	O
well	O
.	O
</s>
<s>
In	O
fact	O
,	O
it	O
seemed	O
that	O
bubble	B-General_Concept
memory	I-General_Concept
would	O
soon	O
be	O
the	O
only	O
form	O
of	O
memory	O
used	O
in	O
the	O
vast	O
majority	O
of	O
applications	O
,	O
with	O
the	O
high-performance	O
market	O
being	O
the	O
only	O
one	O
they	O
could	O
not	O
serve	O
.	O
</s>
<s>
By	O
the	O
mid-1970s	O
,	O
practically	O
every	O
large	O
electronics	O
company	O
had	O
teams	O
working	O
on	O
bubble	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Texas	O
Instruments	O
introduced	O
the	O
first	O
commercial	O
product	O
that	O
incorporated	O
bubble	B-General_Concept
memory	I-General_Concept
in	O
1977	O
,	O
and	O
introduced	O
the	O
first	O
commercially	O
available	O
bubble	B-General_Concept
memory	I-General_Concept
,	O
the	O
TIB	O
0103	O
with	O
92	O
kilobit	O
capacity	O
.	O
</s>
<s>
By	O
the	O
early	O
1980s	O
,	O
however	O
,	O
bubble	B-General_Concept
memory	I-General_Concept
technology	O
became	O
a	O
dead	O
end	O
with	O
the	O
introduction	O
of	O
hard	B-Device
disk	I-Device
systems	O
offering	O
higher	O
storage	B-Device
densities	I-Device
,	O
higher	O
access	O
speeds	O
,	O
and	O
lower	O
costs	O
.	O
</s>
<s>
In	O
1981	O
major	O
companies	O
working	O
on	O
the	O
technology	O
closed	O
their	O
bubble	B-General_Concept
memory	I-General_Concept
operations	O
,	O
notably	O
Rockwell	O
,	O
National	O
Semiconductor	O
,	O
Texas	O
Instruments	O
and	O
Plessey	O
,	O
leaving	O
a	O
"	O
big	O
five	O
"	O
group	O
of	O
companies	O
still	O
pursuing	O
"	O
second-generation	O
bubble	O
"	O
by	O
1984	O
:	O
Intel	O
,	O
Motorola	O
,	O
Hitachi	O
,	O
Sagem	O
and	O
Fujitsu	O
.	O
</s>
<s>
4-megabit	O
bubble	B-General_Concept
memories	I-General_Concept
such	O
as	O
the	O
Intel	O
7114	O
,	O
were	O
introduced	O
in	O
1983	O
and	O
16-megabit	O
bubble	B-General_Concept
memory	I-General_Concept
was	O
developed	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
found	O
uses	O
in	O
niche	O
markets	O
through	O
the	O
1980s	O
in	O
systems	O
needing	O
to	O
avoid	O
the	O
higher	O
rates	O
of	O
mechanical	O
failures	O
of	O
disk	B-Device
drives	I-Device
,	O
and	O
in	O
systems	O
operating	O
in	O
high	O
vibration	O
or	O
harsh	O
environments	O
.	O
</s>
<s>
This	O
application	O
became	O
obsolete	O
too	O
with	O
the	O
development	O
of	O
flash	B-Device
storage	I-Device
,	O
which	O
also	O
brought	O
performance	O
,	O
density	O
,	O
and	O
cost	O
benefits	O
.	O
</s>
<s>
One	O
application	O
was	O
Konami	O
's	O
Bubble	B-Application
System	I-Application
arcade	O
video	O
game	O
system	O
,	O
introduced	O
in	O
1984	O
.	O
</s>
<s>
It	O
featured	O
interchangeable	O
bubble	B-General_Concept
memory	I-General_Concept
cartridges	O
on	O
a	O
68000-based	O
board	O
.	O
</s>
<s>
The	O
Bubble	B-Application
System	I-Application
required	O
a	O
"	O
warm-up	O
"	O
time	O
of	O
about	O
85	O
seconds	O
(	O
prompted	O
by	O
a	O
timer	O
on	O
the	O
screen	O
when	O
switched	O
on	O
)	O
before	O
the	O
game	O
was	O
loaded	O
,	O
as	O
bubble	B-General_Concept
memory	I-General_Concept
needs	O
to	O
be	O
heated	O
to	O
around	O
to	O
operate	O
properly	O
.	O
</s>
<s>
Fujitsu	O
used	O
bubble	B-General_Concept
memory	I-General_Concept
on	O
their	O
FM-8	B-Device
in	O
1981	O
and	O
Sharp	O
used	O
it	O
in	O
their	O
PC	B-Device
5000	I-Device
series	O
,	O
a	O
laptop-like	O
portable	O
computer	O
from	O
1983	O
.	O
</s>
<s>
Nicolet	O
used	O
bubble	B-General_Concept
memory	I-General_Concept
modules	O
for	O
saving	O
waveforms	O
in	O
their	O
Model	O
3091	O
oscilloscope	O
,	O
as	O
did	O
HP	O
who	O
offered	O
a	O
$1595	O
bubble	B-General_Concept
memory	I-General_Concept
option	O
that	O
extended	O
the	O
memory	O
on	O
their	O
model	O
3561A	O
digital	O
signal	O
analyzer	O
.	O
</s>
<s>
TIE	O
communication	O
used	O
it	O
in	O
the	O
early	O
development	O
of	O
digital	O
phone	O
systems	O
in	O
order	O
to	O
lower	O
their	O
MTBF	O
rates	O
and	O
produce	O
a	O
non-volatile	B-General_Concept
telephone	O
system	O
's	O
central	O
processor	O
.	O
</s>
<s>
Bubble	B-General_Concept
memory	I-General_Concept
was	O
also	O
used	O
on	O
the	O
Quantel	O
Mirage	O
DVM8000/1	O
VFX	O
system	O
.	O
</s>
<s>
Bubble	B-General_Concept
memories	I-General_Concept
have	O
extra	O
spare	O
loops	O
to	O
allow	O
for	O
increased	O
yield	O
during	O
manufacturing	O
as	O
they	O
replace	O
defective	O
loops	O
.	O
</s>
<s>
A	O
bubble	B-General_Concept
memory	I-General_Concept
controller	O
will	O
read	O
the	O
boot	O
loop	O
every	O
time	O
a	O
bubble	B-General_Concept
memory	I-General_Concept
system	O
is	O
powered	O
on	O
,	O
during	O
initialization	O
the	O
controller	O
will	O
put	O
the	O
boot	O
loop	O
data	O
in	O
a	O
boot	O
loop	O
register	O
.	O
</s>
<s>
Writing	O
into	O
a	O
bubble	B-General_Concept
memory	I-General_Concept
is	O
done	O
by	O
a	O
formatter	O
within	O
the	O
memory	O
controller	O
and	O
signals	O
from	O
bits	O
read	O
in	O
the	O
bubble	B-General_Concept
memory	I-General_Concept
are	O
amplified	O
by	O
the	O
sense	O
amplifier	O
of	O
the	O
controller	O
and	O
they	O
will	O
reference	O
the	O
boot	O
loop	O
register	O
to	O
avoid	O
overwriting	O
,	O
or	O
further	O
reading	O
of	O
the	O
data	O
in	O
the	O
boot	O
loop	O
.	O
</s>
<s>
If	O
the	O
seed	O
bubble	O
is	O
ever	O
lost	O
,	O
a	O
new	O
one	O
can	O
be	O
nucleated	O
via	O
special	O
signals	O
sent	O
to	O
the	O
bubble	B-General_Concept
memory	I-General_Concept
and	O
a	O
current	O
2	O
to	O
4	O
times	O
higher	O
than	O
necessary	O
for	O
cutting	O
of	O
bubbles	O
from	O
the	O
seed	O
bubble	O
.	O
</s>
<s>
The	O
bubble	O
logic	O
would	O
use	O
nanotechnology	O
and	O
has	O
been	O
demonstrated	O
to	O
have	O
access	O
times	O
of	O
7ms	O
,	O
which	O
is	O
faster	O
than	O
the	O
10ms	O
access	O
times	O
that	O
present	O
hard	B-Device
drives	I-Device
have	O
,	O
though	O
it	O
is	O
slower	O
than	O
the	O
access	O
time	O
of	O
traditional	O
RAM	B-Architecture
and	O
of	O
traditional	O
logic	O
circuits	O
,	O
making	O
the	O
proposal	O
not	O
commercially	O
practical	O
at	O
present	O
.	O
</s>
<s>
IBM	O
's	O
2008	O
work	O
on	O
racetrack	B-General_Concept
memory	I-General_Concept
is	O
essentially	O
a	O
1-dimensional	O
version	O
of	O
bubble	O
,	O
bearing	O
an	O
even	O
closer	O
relationship	O
to	O
the	O
original	O
serial	O
twistor	B-General_Concept
concept	O
.	O
</s>
