<s>
NuBus	B-Device
(	O
pron	O
.	O
</s>
<s>
'	O
New	O
Bus	O
 '	O
)	O
is	O
a	O
32-bit	O
parallel	O
computer	B-General_Concept
bus	I-General_Concept
,	O
originally	O
developed	O
at	O
MIT	O
and	O
standardized	O
in	O
1987	O
as	O
a	O
part	O
of	O
the	O
NuMachine	B-Device
workstation	B-Device
project	O
.	O
</s>
<s>
The	O
first	O
complete	O
implementation	O
of	O
the	O
NuBus	B-Device
was	O
done	O
by	O
Western	O
Digital	O
for	O
their	O
NuMachine	B-Device
,	O
and	O
for	O
the	O
Lisp	B-Operating_System
Machines	I-Operating_System
Inc	O
.	O
LMI	O
Lambda	O
.	O
</s>
<s>
The	O
NuBus	B-Device
was	O
later	O
incorporated	O
in	O
Lisp	O
products	O
by	O
Texas	O
Instruments	O
(	O
Explorer	B-Language
)	O
,	O
and	O
used	O
as	O
the	O
main	O
expansion	B-Device
bus	I-Device
by	O
Apple	O
Computer	O
and	O
a	O
variant	O
called	O
NeXTBus	O
was	O
developed	O
by	O
NeXT	O
.	O
</s>
<s>
Early	O
microcomputer	O
buses	O
like	O
S-100	B-Architecture
were	O
often	O
just	O
connections	O
to	O
the	O
pins	O
of	O
the	O
microprocessor	O
and	O
to	O
the	O
power	O
rails	O
.	O
</s>
<s>
Looking	O
to	O
avoid	O
such	O
problems	O
in	O
the	O
future	O
,	O
NuBus	B-Device
was	O
designed	O
to	O
be	O
independent	O
of	O
the	O
processor	O
,	O
its	O
general	O
architecture	O
and	O
any	O
details	O
of	O
its	O
I/O	B-General_Concept
handling	O
.	O
</s>
<s>
Among	O
its	O
many	O
advanced	O
features	O
for	O
the	O
era	O
,	O
NuBus	B-Device
used	O
a	O
32-bit	O
backplane	O
when	O
8	O
-	O
or	O
16-bit	O
busses	O
were	O
common	O
.	O
</s>
<s>
In	O
addition	O
,	O
NuBus	B-Device
was	O
agnostic	O
about	O
the	O
processor	O
itself	O
.	O
</s>
<s>
NuBus	B-Device
made	O
no	O
such	O
assumptions	O
,	O
which	O
meant	O
that	O
any	O
NuBus	B-Device
card	O
could	O
be	O
plugged	O
into	O
any	O
NuBus	B-Device
machine	O
,	O
as	O
long	O
as	O
there	O
was	O
an	O
appropriate	O
device	B-Application
driver	I-Application
.	O
</s>
<s>
In	O
order	O
to	O
select	O
the	O
proper	O
device	B-Application
driver	I-Application
,	O
NuBus	B-Device
included	O
an	O
ID	O
scheme	O
that	O
allowed	O
the	O
cards	O
to	O
identify	O
themselves	O
to	O
the	O
host	O
computer	O
during	O
startup	O
.	O
</s>
<s>
For	O
instance	O
,	O
with	O
ISA	B-Architecture
the	O
driver	O
had	O
to	O
be	O
configured	O
not	O
only	O
for	O
the	O
card	O
,	O
but	O
for	O
any	O
memory	O
it	O
required	O
,	O
the	O
interrupts	B-Application
it	O
used	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
NuBus	B-Device
required	O
no	O
such	O
configuration	O
,	O
making	O
it	O
one	O
of	O
the	O
first	O
examples	O
of	O
plug-and-play	B-Device
architecture	O
.	O
</s>
<s>
On	O
the	O
downside	O
,	O
while	O
this	O
flexibility	O
made	O
NuBus	B-Device
much	O
simpler	O
for	O
the	O
user	O
and	O
device	B-Application
driver	I-Application
authors	O
,	O
it	O
made	O
things	O
more	O
difficult	O
for	O
the	O
designers	O
of	O
the	O
cards	O
themselves	O
.	O
</s>
<s>
Whereas	O
most	O
"	O
simple	O
"	O
bus	O
systems	O
were	O
easily	O
supported	O
with	O
a	O
handful	O
of	O
input/output	B-General_Concept
chips	O
designed	O
to	O
be	O
used	O
with	O
that	O
CPU	O
in	O
mind	O
,	O
with	O
NuBus	B-Device
every	O
card	O
and	O
computer	O
had	O
to	O
convert	O
everything	O
to	O
a	O
platform-agnostic	O
"	O
NuBus	B-Device
world	O
"	O
.	O
</s>
<s>
Typically	O
this	O
meant	O
adding	O
a	O
NuBus	B-Device
controller	O
chip	O
between	O
the	O
bus	O
and	O
any	O
I/O	B-General_Concept
chips	O
on	O
the	O
card	O
,	O
increasing	O
costs	O
.	O
</s>
<s>
While	O
this	O
is	O
a	O
trivial	O
exercise	O
today	O
,	O
one	O
that	O
all	O
newer	O
buses	O
require	O
,	O
in	O
the	O
1980s	O
NuBus	B-Device
was	O
considered	O
needlessly	O
complex	O
and	O
expensive	O
.	O
</s>
<s>
The	O
NuBus	B-Device
became	O
a	O
standard	O
in	O
1987	O
as	O
IEEE	O
1196	O
.	O
</s>
<s>
A	O
later	O
addition	O
,	O
NuBus	B-Device
90	I-Device
,	O
increased	O
the	O
clock	O
rate	O
to	O
20MHz	O
for	O
better	O
throughput	O
,	O
burst	O
increasing	O
to	O
about	O
70	O
MB/s	O
,	O
and	O
average	O
to	O
about	O
30	O
MB/s	O
.	O
</s>
<s>
The	O
NuBus	B-Device
was	O
first	O
developed	O
commercially	O
in	O
the	O
Western	B-Device
Digital	I-Device
NuMachine	I-Device
,	O
and	O
first	O
used	O
in	O
a	O
production	O
product	O
by	O
their	O
licensee	O
,	O
Lisp	B-Operating_System
Machines	I-Operating_System
,	O
Inc.	O
,	O
in	O
the	O
LMI-Lambda	O
,	O
a	O
Lisp	B-Operating_System
Machine	I-Operating_System
.	O
</s>
<s>
The	O
technology	O
was	O
incorporated	O
into	O
their	O
TI	B-Language
Explorer	I-Language
,	O
also	O
a	O
Lisp	B-Operating_System
Machine	I-Operating_System
.	O
</s>
<s>
In	O
1986	O
,	O
Texas	O
Instruments	O
used	O
the	O
NuBus	B-Device
in	O
the	O
S1500	O
multiprocessor	O
UNIX	O
system	O
.	O
</s>
<s>
Later	O
,	O
both	O
Texas	O
Instruments	O
and	O
Symbolics	O
developed	O
Lisp	B-Operating_System
Machine	I-Operating_System
NuBus	B-Device
boards	O
(	O
the	O
TI	O
MicroExplorer	O
and	O
the	O
Symbolics	O
MacIvory	O
)	O
based	O
on	O
their	O
Lisp	O
supporting	O
microprocessors	O
.	O
</s>
<s>
These	O
NuBus	B-Device
boards	O
were	O
co-processor	O
Lisp	B-Operating_System
Machines	I-Operating_System
for	O
the	O
Apple	B-Device
Macintosh	I-Device
line	O
(	O
the	O
Mac	B-Device
II	I-Device
and	O
Mac	B-Device
Quadras	I-Device
)	O
.	O
</s>
<s>
NuBus	B-Device
was	O
also	O
selected	O
by	O
Apple	O
Computer	O
for	O
use	O
in	O
their	O
Macintosh	B-Device
II	I-Device
project	O
,	O
where	O
its	O
plug-n-play	B-Device
nature	O
fit	O
well	O
with	O
the	O
Mac	B-Device
philosophy	O
of	O
ease-of-use	O
.	O
</s>
<s>
It	O
was	O
used	O
in	O
most	O
of	O
the	O
Macintosh	B-Device
II	I-Device
series	I-Device
that	O
made	O
up	O
the	O
professional-level	O
Mac	B-Device
lineup	O
from	O
the	O
late	O
1980s	O
.	O
</s>
<s>
It	O
was	O
upgraded	O
to	O
NuBus	B-Device
90	I-Device
starting	O
with	O
the	O
Macintosh	B-Device
Quadras	I-Device
and	O
used	O
into	O
the	O
mid-1990s	O
.	O
</s>
<s>
This	O
was	O
later	O
addressed	O
in	O
the	O
NuBus	B-Device
implementation	O
on	O
the	O
660AV	O
and	O
840AV	O
models	O
.	O
</s>
<s>
This	O
improved	O
NuBus	B-Device
controller	O
was	O
used	O
in	O
the	O
first	O
generation	O
Power	B-Device
Macintosh	I-Device
6100	I-Device
,	O
7100	B-Device
and	O
8100	B-Device
models	O
.	O
</s>
<s>
Later	O
Power	O
Mac	B-Device
models	O
adopted	O
Intel	O
's	O
PCI	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
Apple	O
's	O
NuBus	B-Device
implementation	O
used	O
pin	O
and	O
socket	O
connectors	O
on	O
the	O
back	O
of	O
the	O
card	O
rather	O
than	O
edge	O
connectors	O
with	O
Phillips	O
screws	O
inside	O
the	O
case	O
that	O
most	O
cards	O
use	O
,	O
making	O
it	O
much	O
easier	O
to	O
install	O
cards	O
.	O
</s>
<s>
This	O
was	O
apparently	O
part	O
of	O
an	O
unapproved	O
NuBus	B-Device
standard	O
.	O
</s>
<s>
NuBus	B-Device
was	O
also	O
selected	O
by	O
NeXT	B-Device
Computer	I-Device
for	O
their	O
line	O
of	O
machines	O
,	O
but	O
used	O
a	O
different	O
physical	O
PCB	O
layout	O
.	O
</s>
<s>
NuBus	B-Device
appears	O
to	O
have	O
seen	O
little	O
use	O
outside	O
these	O
roles	O
,	O
and	O
when	O
Apple	O
switched	O
to	O
PCI	B-Protocol
in	O
the	O
mid	O
1990s	O
,	O
NuBus	B-Device
quickly	O
disappeared	O
.	O
</s>
