<s>
Hybrid	B-Device
computers	I-Device
are	O
computers	O
that	O
exhibit	O
features	O
of	O
analog	O
computers	O
and	O
digital	O
computers	O
.	O
</s>
<s>
The	O
digital	O
component	O
normally	O
serves	O
as	O
the	O
controller	O
and	O
provides	O
logical	O
and	O
numerical	B-General_Concept
operations	O
,	O
while	O
the	O
analog	O
component	O
often	O
serves	O
as	O
a	O
solver	O
of	O
differential	O
equations	O
and	O
other	O
mathematically	O
complex	O
problems	O
.	O
</s>
<s>
Another	O
early	O
example	O
was	O
the	O
HYDAC	O
2400	O
,	O
an	O
integrated	O
hybrid	B-Device
computer	I-Device
released	O
by	O
EAI	O
in	O
1963	O
.	O
</s>
<s>
In	O
the	O
1980s	O
,	O
Marconi	O
Space	O
and	O
Defense	O
Systems	O
Limited	O
(	O
under	O
Peggy	O
Hodges	O
)	O
developed	O
their	O
"	O
Starglow	O
Hybrid	B-Device
Computer	I-Device
"	O
,	O
which	O
consisted	O
of	O
three	O
EAI	O
8812	O
analog	O
computers	O
linked	O
to	O
an	O
EAI	O
8100	O
digital	O
computer	O
,	O
the	O
latter	O
also	O
being	O
linked	O
to	O
an	O
SEL	O
3200	O
digital	O
computer	O
.	O
</s>
<s>
Late	O
in	O
the	O
20th	O
century	O
,	O
hybrids	O
dwindled	O
with	O
the	O
increasing	O
capabilities	O
of	O
digital	O
computers	O
including	O
digital	B-Architecture
signal	I-Architecture
processors	I-Architecture
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
precision	B-Architecture
of	O
analog	O
computers	O
is	O
not	O
good	O
;	O
they	O
are	O
limited	O
to	O
three	O
,	O
or	O
at	O
most	O
,	O
four	O
digits	O
of	O
precision	B-Architecture
.	O
</s>
<s>
Digital	O
computers	O
can	O
be	O
built	O
to	O
take	O
the	O
solution	O
of	O
equations	O
to	O
almost	O
unlimited	O
precision	B-Architecture
,	O
but	O
quite	O
slowly	O
compared	O
to	O
analog	O
computers	O
.	O
</s>
<s>
Generally	O
,	O
complex	O
mathematical	O
equations	O
are	O
approximated	O
using	O
iterative	B-Algorithm
methods	I-Algorithm
which	O
take	O
huge	O
numbers	O
of	O
iterations	O
,	O
depending	O
on	O
how	O
good	O
the	O
initial	O
"	O
guess	O
"	O
at	O
the	O
final	O
value	O
is	O
and	O
how	O
much	O
precision	B-Architecture
is	O
desired	O
.	O
</s>
<s>
(	O
This	O
initial	O
guess	O
is	O
known	O
as	O
the	O
numerical	B-General_Concept
"	O
seed	O
"	O
.	O
)	O
</s>
<s>
For	O
many	O
real-time	B-General_Concept
operations	O
in	O
the	O
20th	O
century	O
,	O
such	O
digital	O
calculations	O
were	O
too	O
slow	O
to	O
be	O
of	O
much	O
use	O
(	O
e.g.	O
,	O
for	O
very	O
high	O
frequency	O
phased	B-Algorithm
array	I-Algorithm
radars	I-Algorithm
or	O
for	O
weather	O
calculations	O
)	O
,	O
but	O
the	O
precision	B-Architecture
of	O
an	O
analog	O
computer	O
is	O
insufficient	O
.	O
</s>
<s>
Hybrid	B-Device
computers	I-Device
can	O
be	O
used	O
to	O
obtain	O
a	O
very	O
good	O
but	O
relatively	O
imprecise	O
'	O
seed	O
 '	O
value	O
,	O
using	O
an	O
analog	O
computer	O
front-end	O
,	O
which	O
is	O
then	O
fed	O
into	O
a	O
digital	O
computer	O
iterative	O
process	O
to	O
achieve	O
the	O
final	O
desired	O
degree	O
of	O
precision	B-Architecture
.	O
</s>
<s>
With	O
a	O
three	O
or	O
four	O
digit	O
,	O
highly	O
accurate	O
numerical	B-General_Concept
seed	O
,	O
the	O
total	O
digital	O
computation	O
time	O
to	O
reach	O
the	O
desired	B-Architecture
precision	I-Architecture
is	O
dramatically	O
reduced	O
,	O
since	O
many	O
fewer	O
iterations	O
are	O
required	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
technical	O
problems	O
to	O
be	O
overcome	O
in	O
hybrid	B-Device
computers	I-Device
is	O
minimizing	O
digital-computer	O
noise	O
in	O
analog	O
computing	O
elements	O
and	O
grounding	O
systems	O
.	O
</s>
<s>
Consider	O
that	O
the	O
nervous	O
system	O
in	O
animals	O
is	O
a	O
form	O
of	O
hybrid	B-Device
computer	I-Device
.	O
</s>
<s>
Signals	O
pass	O
across	O
the	O
synapses	B-Application
from	O
one	O
nerve	O
cell	O
to	O
the	O
next	O
as	O
discrete	O
(	O
digital	O
)	O
packets	O
of	O
chemicals	O
,	O
which	O
are	O
then	O
summed	O
within	O
the	O
nerve	O
cell	O
in	O
an	O
analog	O
fashion	O
by	O
building	O
an	O
electro-chemical	O
potential	O
until	O
its	O
threshold	B-Algorithm
is	O
reached	O
,	O
whereupon	O
it	O
discharges	O
and	O
sends	O
out	O
a	O
series	O
of	O
digital	O
packets	O
to	O
the	O
next	O
nerve	O
cell	O
.	O
</s>
<s>
The	O
individual	O
nerve	O
cells	O
are	O
analogous	O
to	O
analog	O
computers	O
;	O
the	O
synapses	B-Application
are	O
analogous	O
to	O
digital	O
computers	O
.	O
</s>
<s>
Hybrid	B-Device
computers	I-Device
are	O
distinct	O
from	O
hybrid	O
systems	O
.	O
</s>
<s>
In	O
2015	O
,	O
researchers	O
at	O
Columbia	O
University	O
published	O
a	O
paper	O
on	O
a	O
small	O
scale	O
hybrid	B-Device
computer	I-Device
in	O
65nm	O
CMOS	O
technology	O
.	O
</s>
<s>
This	O
4th-order	O
VLSI	O
hybrid	B-Device
computer	I-Device
contains	O
4	O
integrator	O
blocks	O
,	O
8	O
multiplier/gain	O
-setting	O
blocks	O
,	O
8	O
fanout	O
blocks	O
for	O
distributing	O
current-mode	O
signals	O
,	O
2	O
ADCs	O
,	O
2	O
DACs	O
and	O
2	O
SRAMs	O
blocks	O
.	O
</s>
