<s>
Bit	B-General_Concept
slicing	I-General_Concept
is	O
a	O
technique	O
for	O
constructing	O
a	O
processor	B-General_Concept
from	O
modules	O
of	O
processors	O
of	O
smaller	O
bit	O
width	O
,	O
for	O
the	O
purpose	O
of	O
increasing	O
the	O
word	O
length	O
;	O
in	O
theory	O
to	O
make	O
an	O
arbitrary	O
n-bit	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	B-General_Concept
)	O
.	O
</s>
<s>
Bit	B-General_Concept
slicing	I-General_Concept
more	O
or	O
less	O
died	O
out	O
due	O
to	O
the	O
advent	O
of	O
the	O
microprocessor	B-Architecture
.	O
</s>
<s>
Recently	O
it	O
has	O
been	O
used	O
in	O
arithmetic	B-General_Concept
logic	I-General_Concept
units	I-General_Concept
(	O
ALUs	O
)	O
for	O
quantum	B-Architecture
computers	I-Architecture
and	O
as	O
a	O
software	O
technique	O
,	O
e.g.	O
</s>
<s>
for	O
cryptography	O
in	O
x86	B-Operating_System
CPUs	O
.	O
</s>
<s>
Bit-slice	B-General_Concept
processors	I-General_Concept
(	O
BSPs	O
)	O
usually	O
include	O
1-	O
,	O
2-	O
,	O
4-	O
,	O
8	O
-	O
or	O
16-bit	B-Device
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	O
)	O
and	O
control	O
lines	O
(	O
including	O
carry	B-Algorithm
or	O
overflow	B-Algorithm
signals	O
that	O
are	O
internal	O
to	O
the	O
processor	B-General_Concept
in	O
non-bitsliced	O
CPU	B-General_Concept
designs	O
)	O
.	O
</s>
<s>
three	O
1-bit	O
units	O
can	O
make	O
a	O
3-bit	O
ALU	O
,	O
thus	O
3-bit	O
(	O
or	O
n-bit	O
)	O
CPU	B-General_Concept
,	O
while	O
3-bit	O
,	O
or	O
any	O
CPU	B-General_Concept
with	O
higher	O
odd	O
number	O
of	O
bits	O
,	O
has	O
n't	O
been	O
manufactured	O
and	O
sold	O
in	O
volume	O
)	O
.	O
</s>
<s>
Four	O
4-bit	O
ALU	O
chips	O
could	O
be	O
used	O
to	O
build	O
a	O
16-bit	B-Device
ALU	O
.	O
</s>
<s>
A	O
microsequencer	B-General_Concept
or	O
control	O
ROM	O
would	O
be	O
used	O
to	O
execute	O
logic	O
to	O
provide	O
data	O
and	O
control	O
signals	O
to	O
regulate	O
function	O
of	O
the	O
component	O
ALUs	O
.	O
</s>
<s>
Known	O
bit-slice	B-General_Concept
microprocessors	I-General_Concept
:	O
</s>
<s>
Intel	B-General_Concept
3000	I-General_Concept
family	O
(	O
1974	O
,	O
now	O
discontinued	O
)	O
,	O
e.g.	O
</s>
<s>
National	B-Device
IMP-16	I-Device
,	O
a	O
16-bit	B-Device
processor	I-Device
based	O
on	O
the	O
IMP	O
chipset	O
,	O
e.g.	O
</s>
<s>
AMD	B-General_Concept
Am2900	I-General_Concept
family	O
(	O
1975	O
)	O
,	O
e.g.	O
</s>
<s>
Motorola	B-Device
M10800	I-Device
family	O
(	O
1979	O
)	O
,	O
e.g.	O
</s>
<s>
Raytheon	O
RP-16	O
,	O
a	O
16-bit	B-Device
processor	I-Device
consisting	O
of	O
seven	O
integrated	O
circuits	O
,	O
using	O
four	O
RALU	O
chips	O
and	O
three	O
CROM	O
chips	O
.	O
</s>
<s>
16-bit	B-Device
slice	O
:	O
</s>
<s>
Bit	B-General_Concept
slicing	I-General_Concept
,	O
although	O
not	O
called	O
that	O
at	O
the	O
time	O
,	O
was	O
also	O
used	O
in	O
computers	O
before	O
large-scale	O
integrated	O
circuits	O
(	O
LSI	O
,	O
the	O
predecessor	O
to	O
today	O
's	O
VLSI	O
,	O
or	O
very-large-scale	O
integration	O
circuits	O
)	O
.	O
</s>
<s>
The	O
first	O
bit-sliced	O
machine	O
was	O
EDSAC	B-Device
2	I-Device
,	O
built	O
at	O
the	O
University	O
of	O
Cambridge	O
Mathematical	O
Laboratory	O
in	O
1956	O
–	O
1958	O
.	O
</s>
<s>
While	O
32-bit	O
microprocessors	B-Architecture
were	O
being	O
discussed	O
at	O
the	O
time	O
,	O
few	O
were	O
in	O
production	O
.	O
</s>
<s>
The	O
UNIVAC	O
1100	O
series	O
mainframes	O
(	O
one	O
of	O
the	O
oldest	O
series	O
,	O
originating	O
in	O
the	O
1950s	O
)	O
has	O
a	O
36-bit	O
architecture	O
,	O
and	O
the	O
1100/60	O
introduced	O
in	O
1979	O
used	O
nine	O
Motorola	B-Device
MC10800	I-Device
4-bit	O
ALU	O
chips	O
to	O
implement	O
the	O
needed	O
word	O
width	O
while	O
using	O
modern	O
integrated	O
circuits	O
.	O
</s>
<s>
At	O
the	O
time	O
16-bit	B-Device
processors	I-Device
were	O
common	O
but	O
expensive	O
,	O
and	O
8-bit	O
processors	O
,	O
such	O
as	O
the	O
Z80	B-General_Concept
,	O
were	O
widely	O
used	O
in	O
the	O
nascent	O
home-computer	O
market	O
.	O
</s>
<s>
Combining	O
components	O
to	O
produce	O
bit-slice	B-General_Concept
products	O
allowed	O
engineers	O
and	O
students	O
to	O
create	O
more	O
powerful	O
and	O
complex	O
computers	O
at	O
a	O
more	O
reasonable	O
cost	O
,	O
using	O
off-the-shelf	O
components	O
that	O
could	O
be	O
custom-configured	O
.	O
</s>
<s>
The	O
main	O
advantage	O
was	O
that	O
bit	B-General_Concept
slicing	I-General_Concept
made	O
it	O
economically	O
possible	O
in	O
smaller	O
processors	O
to	O
use	O
bipolar	O
transistors	O
,	O
which	O
switch	O
much	O
faster	O
than	O
NMOS	B-Algorithm
or	O
CMOS	B-Device
transistors	O
.	O
</s>
<s>
This	O
allowed	O
much	O
higher	O
clock	O
rates	O
,	O
where	O
speed	O
was	O
needed	O
for	O
example	O
,	O
for	O
DSP	B-General_Concept
functions	O
or	O
matrix	B-Algorithm
transformation	I-Algorithm
or	O
,	O
as	O
in	O
the	O
Xerox	B-Device
Alto	I-Device
,	O
the	O
combination	O
of	O
flexibility	O
and	O
speed	O
,	O
before	O
discrete	O
CPUs	O
were	O
able	O
to	O
deliver	O
that	O
.	O
</s>
<s>
In	O
more	O
recent	O
times	O
,	O
the	O
term	O
bit	B-General_Concept
slicing	I-General_Concept
was	O
reused	O
by	O
Matthew	O
Kwan	O
to	O
refer	O
to	O
the	O
technique	O
of	O
using	O
a	O
general-purpose	O
CPU	B-General_Concept
to	O
implement	O
multiple	O
parallel	O
simple	O
virtual	B-Architecture
machines	I-Architecture
using	O
general	O
logic	O
instructions	O
to	O
perform	O
single-instruction	O
multiple-data	O
(	O
SIMD	B-Device
)	O
operations	O
.	O
</s>
<s>
This	O
technique	O
is	O
also	O
known	O
as	O
SIMD	B-General_Concept
within	I-General_Concept
a	I-General_Concept
register	I-General_Concept
(	O
SWAR	B-General_Concept
)	O
.	O
</s>
<s>
This	O
was	O
initially	O
in	O
reference	O
to	O
Eli	O
Biham	O
's	O
1997	O
article	O
A	O
Fast	O
New	O
DES	B-Algorithm
Implementation	O
in	O
Software	O
,	O
which	O
achieved	O
significant	O
gains	O
in	O
performance	O
of	O
DES	B-Algorithm
by	O
using	O
this	O
method	O
.	O
</s>
<s>
To	O
simplify	O
the	O
circuit	O
structure	O
and	O
reduce	O
the	O
hardware	O
cost	O
of	O
quantum	B-Architecture
computers	I-Architecture
(	O
proposed	O
to	O
run	O
the	O
MIPS32	B-Device
instruction	I-Device
set	I-Device
)	O
a	O
50GHz	O
superconducting	O
"	O
4-bit	O
bit-slice	B-General_Concept
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	O
)	O
for	O
32-bit	O
rapid	O
single-flux-quantum	O
microprocessors	B-Architecture
was	O
demonstrated	O
"	O
.	O
</s>
