<s>
The	O
Motorola	B-General_Concept
68881	I-General_Concept
and	O
Motorola	B-General_Concept
68882	I-General_Concept
are	O
floating-point	B-General_Concept
units	I-General_Concept
(	O
FPUs	O
)	O
used	O
in	O
some	O
computer	O
systems	O
in	O
conjunction	O
with	O
Motorola	O
's	O
32-bit	O
68020	B-Device
or	O
68030	B-Device
microprocessors	I-Device
.	O
</s>
<s>
The	O
Motorola	B-General_Concept
68881	I-General_Concept
was	O
introduced	O
in	O
1984	O
.	O
</s>
<s>
The	O
68882	B-General_Concept
is	O
a	O
higher	O
performance	O
version	O
produced	O
later	O
.	O
</s>
<s>
The	O
68020	B-Device
and	O
68030	B-Device
CPUs	O
were	O
designed	O
with	O
the	O
separate	O
68881	B-General_Concept
chip	O
in	O
mind	O
.	O
</s>
<s>
Their	O
instruction	O
sets	O
reserved	O
the	O
"	O
F-line	O
"	O
instructions	O
–	O
that	O
is	O
,	O
all	O
opcodes	B-Language
beginning	O
with	O
the	O
hexadecimal	O
digit	O
"	O
F	O
"	O
could	O
either	O
be	O
forwarded	O
to	O
an	O
external	O
coprocessor	O
or	O
be	O
used	O
as	O
"	O
traps	B-Application
"	O
which	O
would	O
throw	O
an	O
exception	B-Application
,	O
handing	O
control	O
to	O
the	O
computer	O
's	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
If	O
an	O
FPU	O
is	O
not	O
present	O
in	O
the	O
system	O
,	O
the	O
OS	O
would	O
then	O
either	O
call	O
an	O
FPU	O
emulator	B-Application
to	O
execute	O
the	O
instruction	O
's	O
equivalent	O
using	O
68020	B-Device
integer-based	O
software	O
code	O
,	O
return	O
an	O
error	O
to	O
the	O
program	O
,	O
terminate	O
the	O
program	O
,	O
or	O
crash	O
and	O
require	O
a	O
reboot	O
.	O
</s>
<s>
The	O
68881	B-General_Concept
has	O
eight	O
80-bit	O
data	O
registers[2][3]	O
(	O
a	O
64-bit	O
mantissa	O
plus	O
a	O
sign	O
bit	O
,	O
and	O
a	O
15-bit	O
signed	O
exponent	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
when	O
an	O
instruction	O
requires	O
any	O
address	O
calculations	O
,	O
the	O
main	O
CPU	O
handles	O
them	O
before	O
the	O
68881	B-General_Concept
takes	O
control	O
.	O
</s>
<s>
When	O
the	O
CPU	O
encounters	O
a	O
68881	B-General_Concept
instruction	O
,	O
it	O
hands	O
the	O
FPU	O
all	O
operands	O
needed	O
for	O
that	O
instruction	O
,	O
and	O
then	O
the	O
FPU	O
releases	O
the	O
CPU	O
to	O
go	O
on	O
and	O
execute	O
the	O
next	O
instruction	O
.	O
</s>
<s>
The	O
68882	B-General_Concept
is	O
an	O
improved	O
version	O
of	O
the	O
68881	B-General_Concept
,	O
with	O
better	O
pipelining	B-General_Concept
,	O
and	O
eventually	O
available	O
at	O
higher	O
clock	O
speeds	O
.	O
</s>
<s>
Motorola	O
claimed	O
in	O
some	O
marketing	O
literature	O
that	O
it	O
executes	O
some	O
instructions	O
40%	O
faster	O
than	O
a	O
68881	B-General_Concept
at	O
the	O
same	O
clock	O
speed	O
,	O
though	O
this	O
did	O
not	O
reflect	O
typical	O
performance	O
,	O
as	O
seen	O
by	O
its	O
more	O
modest	O
improvement	O
in	O
the	O
table	O
below	O
.	O
</s>
<s>
The	O
68882	B-General_Concept
is	O
pin	O
compatible	O
with	O
the	O
68881	B-General_Concept
and	O
can	O
be	O
used	O
as	O
a	O
direct	O
replacement	O
in	O
most	O
systems	O
.	O
</s>
<s>
The	O
most	O
important	O
software	O
incompatibility	O
is	O
that	O
the	O
68882	B-General_Concept
uses	O
a	O
larger	O
FSAVE	O
state	O
frame	O
,	O
which	O
affects	O
UNIX	B-Application
and	O
other	O
preemptive	O
multitasking	O
OSes	O
that	O
had	O
to	O
be	O
modified	O
to	O
allocate	O
more	O
space	O
for	O
it	O
.	O
</s>
<s>
The	O
68881	B-General_Concept
or	O
68882	B-General_Concept
were	O
used	O
in	O
the	O
Sun	O
Microsystems	O
Sun-3	B-Device
workstations	I-Device
,	O
IBM	B-Device
RT	I-Device
PC	I-Device
workstations	O
,	O
Apple	O
Computer	O
Macintosh	B-Device
II	I-Device
family	O
,	O
NeXT	B-Device
Computer	I-Device
,	O
Sharp	B-Device
X68000	I-Device
,	O
Amiga	B-Device
3000	I-Device
,	O
Convergent	O
Technologies	O
MightyFrame	O
,	O
Atari	B-Device
Mega	I-Device
STE	I-Device
,	O
TT	B-Device
,	O
and	O
Falcon	B-Device
.	O
</s>
<s>
Some	O
third-party	O
Amiga	O
and	O
Atari	O
products	O
used	O
the	O
68881	B-General_Concept
or	O
68882	B-General_Concept
as	O
a	O
memory-mapped	B-Architecture
peripheral	O
to	O
the	O
68000	B-Device
.	O
</s>
<s>
No	O
statistics	O
are	O
listed	O
for	O
the	O
16MHz	O
and	O
20MHz	O
68882	B-General_Concept
,	O
though	O
these	O
chips	O
were	O
indeed	O
produced	O
.	O
</s>
<s>
Starting	O
with	O
the	O
Motorola	B-Device
68040	I-Device
,	O
floating	O
point	O
support	O
was	O
included	O
in	O
the	O
CPU	O
itself	O
.	O
</s>
