<s>
Software	O
development	O
for	O
the	O
Cell	O
microprocessor	O
involves	O
a	O
mixture	O
of	O
conventional	O
development	O
practices	O
for	O
the	O
PowerPC-compatible	O
PPU	O
core	O
,	O
and	O
novel	O
software	O
development	O
challenges	O
with	O
regard	O
to	O
the	O
functionally	O
reduced	O
SPU	O
coprocessors	O
.	O
</s>
<s>
An	O
open	O
source	O
software-based	O
strategy	O
was	O
adopted	O
to	O
accelerate	O
the	O
development	O
of	O
a	O
Cell	O
BE	O
ecosystem	O
and	O
to	O
provide	O
an	O
environment	O
to	O
develop	O
Cell	O
applications	O
,	O
including	O
a	O
GCC-based	O
Cell	O
compiler	B-Language
,	O
binutils	O
and	O
a	O
port	O
of	O
the	O
Linux	O
operating	O
system	O
.	O
</s>
<s>
Octopiler	B-General_Concept
is	O
IBM	O
's	O
prototype	O
compiler	B-Language
to	O
allow	O
software	B-Application
developers	I-Application
to	O
write	O
code	B-Application
for	O
Cell	O
processors	O
.	O
</s>
<s>
The	O
VMX	B-General_Concept
(	O
Vector	B-General_Concept
Multimedia	I-General_Concept
Extensions	I-General_Concept
)	O
technology	O
is	O
conceptually	O
similar	O
to	O
the	O
vector	O
model	O
provided	O
by	O
the	O
SPU	O
processors	O
,	O
but	O
there	O
are	O
many	O
significant	O
differences	O
.	O
</s>
<s>
The	O
VMX	B-General_Concept
Java	B-Language
mode	O
conforms	O
to	O
the	O
Java	B-Language
Language	I-Language
Specification	I-Language
1	O
subset	O
of	O
the	O
default	O
IEEE	O
Standard	O
,	O
extended	O
to	O
include	O
IEEE	O
and	O
C9X	B-Language
compliance	O
where	O
the	O
Java	B-Language
standard	O
falls	O
silent	O
.	O
</s>
<s>
In	O
a	O
typical	O
implementation	O
,	O
non-Java	O
mode	O
converts	O
denormal	B-Algorithm
values	O
to	O
zero	O
but	O
Java	B-Language
mode	O
traps	O
into	O
an	O
emulator	O
when	O
the	O
processor	O
encounters	O
such	O
a	O
value	O
.	O
</s>
<s>
The	O
IBM	O
PPE	O
Vector/SIMD	O
manual	O
does	O
not	O
define	O
operations	O
for	O
double-precision	O
floating	B-Algorithm
point	I-Algorithm
,	O
though	O
IBM	O
has	O
published	O
material	O
implying	O
certain	O
double-precision	O
performance	O
numbers	O
associated	O
with	O
the	O
Cell	O
PPE	O
VMX	B-General_Concept
technology	O
.	O
</s>
<s>
Compilers	B-Language
for	O
Cell	O
provide	O
intrinsics	O
to	O
expose	O
useful	O
SPU	O
instructions	O
in	O
C	O
and	O
C++	O
.	O
</s>
<s>
Instructions	O
that	O
differ	O
only	O
in	O
the	O
type	O
of	O
operand	O
(	O
such	O
as	O
a	O
,	O
ai	O
,	O
ah	O
,	O
ahi	O
,	O
fa	O
,	O
and	O
dfa	O
for	O
addition	O
)	O
are	O
typically	O
represented	O
by	O
a	O
single	O
C/C	O
++	O
intrinsic	B-Application
which	O
selects	O
the	O
proper	O
instruction	O
based	O
on	O
the	O
type	O
of	O
the	O
operand	O
.	O
</s>
<s>
There	O
is	O
a	O
great	O
body	O
of	O
code	B-Application
which	O
has	O
been	O
developed	O
for	O
other	O
IBM	B-Device
Power	I-Device
microprocessors	I-Device
that	O
could	O
potentially	O
be	O
adapted	O
and	O
recompiled	B-Language
to	O
run	O
on	O
the	O
SPU	O
.	O
</s>
<s>
This	O
code	B-Application
base	O
includes	O
VMX	B-General_Concept
code	B-Application
that	O
runs	O
under	O
the	O
PowerPC	B-Architecture
version	O
of	O
Apple	O
's	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
,	O
where	O
it	O
is	O
better	O
known	O
as	O
Altivec	B-General_Concept
.	O
</s>
<s>
Depending	O
on	O
how	O
many	O
VMX	B-General_Concept
specific	O
features	O
are	O
involved	O
,	O
the	O
adaptation	O
involved	O
can	O
range	O
anywhere	O
from	O
straightforward	O
,	O
to	O
onerous	O
,	O
to	O
completely	O
impractical	O
.	O
</s>
<s>
In	O
some	O
cases	O
it	O
is	O
possible	O
to	O
port	O
existing	O
VMX	B-General_Concept
code	B-Application
directly	O
.	O
</s>
<s>
If	O
the	O
VMX	B-General_Concept
code	B-Application
is	O
highly	O
generic	O
(	O
makes	O
few	O
assumptions	O
about	O
the	O
execution	O
environment	O
)	O
the	O
translation	O
can	O
be	O
relatively	O
straightforward	O
.	O
</s>
<s>
The	O
two	O
processors	O
specify	O
a	O
different	O
binary	O
code	B-Application
format	O
,	O
so	O
recompilation	O
is	O
required	O
at	O
a	O
minimum	O
.	O
</s>
<s>
IBM	O
provides	O
compiler	B-Language
intrinsics	O
which	O
take	O
care	O
of	O
this	O
mapping	O
transparently	O
as	O
part	O
of	O
the	O
development	O
toolkit	O
.	O
</s>
<s>
At	O
the	O
other	O
extreme	O
,	O
if	O
Java	B-Language
floating-point	B-Algorithm
semantics	O
are	O
required	O
,	O
this	O
is	O
almost	O
impossible	O
to	O
achieve	O
on	O
the	O
SPU	O
processor	O
.	O
</s>
<s>
The	O
most	O
important	O
conceptual	O
similarity	O
between	O
VMX	B-General_Concept
and	O
the	O
SPU	O
architecture	O
is	O
supporting	O
the	O
same	O
vectorization	O
model	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
most	O
algorithms	O
adapted	O
to	O
Altivec	B-General_Concept
will	O
usually	O
adapt	O
successfully	O
to	O
the	O
SPU	O
architecture	O
as	O
well	O
.	O
</s>
