A
AirRaid
Intel's Larrabee GPU based on secret Pentagon tech, sorta [Updated]
By Jon Stokes
In a recent interview with German tech site heise.de, Intel's Pat
Gelsinger let slip* there's some interesting information that I've
been sitting on since last year, but haven't published: the processor
cores that make up Intel's forthcoming Larrabee GPU are based on the
original Pentium core design. Larrabee is, in essence, a bunch of P54C
(i.e. pre-MMX) Pentium cores that have been enhanced with very wide
vector floating-point resources and ganged together to make the brains
of a flexible, x86-based GPU.
*Update: Intel contacted me to clarify that Gelsinger did not, in
fact, tell heise.de that Larrabee was based on P54C. This was
something that was apparently mangled in the Babelfish translation,
and Andreas at heise.de was pulling the P54C detail from some other
source. Nonetheless, I had already heard the information about the
Larrabee-Pentium-Pentagon connection from a source of my own, so I do
vouch for it.
You're probably wondering why Intel picked the old P54C to base
Larrabee off of, instead of, say, the later P55 part with MMX. The
reason, which Gelsinger did not reveal to heise.de and which comes
from a source of mine, is a bit surprising, in that it involves the
Pentagon.
Say "Pentagon Pentium" five times fast
Quite some time ago, after the Pentium was obsolete and Intel had
moved on, the company gave the RTL code for the processor to the
Pentagon so that the military could continue to fabricate a radiation
hardened version of it for use in military applications. Trailing-edge
hardware like the Pentium has the advantage of having been thoroughly
tested and debugged (cf. the P54C's infamous FDIV bug), and at the
time the military had its own fab facilities that could do some low-
volume fabrication. (I'm sure they still have such facilities for
prototyping.) So the Pentagon cleaned up the P54C's RTL code and began
producing a rad-hard version of the chip for military use.
A few years later, when the Pentagon had moved on from the P54C, they
offered the RTL back to Intel. So Intel took the core, which has a
very small footprint and by this time had been pretty thoroughly
debugged, and modified it for use in the many-core chip that later
became Larrabee.
Speaking of five times fast
While I'm just spilling all kinds of Larrabee beans, I might as well
drop another, performance-related tidbit that came my way. In an
upcoming SIGGRAPH paper, Intel will claim that Larrabee has 20x the
performance per watt of a Core 2 Duo and half the single-threaded
performance. It also has a 4MB coherent L2, and three-operand vector
instructions.
Note that I don't have any more context for the information I just
gave, so I'm not sure if "half the performance of Core 2 Duo" is a
clock-for-clock figure or not. If it is, recall that the Pentium's
pipeline is less than half the depth of Core 2's, so if the GPU does
debut in the 1.7GHz to 2.5GHz range, then that will help it in Core 2
comparisons. The other big unknown is the type of workload that Intel
is using for this ballpark performance figure. When it comes to in-
order (i.e., Larrabee) vs. out-of-order (i.e., Core 2) and short
pipeline vs. long pipeline, the type of workload involved makes all
the difference. So these few details that I've given tell you a lot
less than you might think at first; but something is better than
nothing—and nothing is what we have so far about Larrabee's
peformance.
http://arstechnica.com/news.ars/pos...-gpu-based-on-secret-pentagon-tech-sorta.html
Hmmm
If Intel is using old Pentium CPU technology in Larrabee, I hope they
also use old GPU tech for the rasterisation portions of the chip.
Specifically, Lockheed Martin Real3D graphics technology, which Intel
once owned the patents to, and probably still has knowledge of.
By Jon Stokes
In a recent interview with German tech site heise.de, Intel's Pat
Gelsinger let slip* there's some interesting information that I've
been sitting on since last year, but haven't published: the processor
cores that make up Intel's forthcoming Larrabee GPU are based on the
original Pentium core design. Larrabee is, in essence, a bunch of P54C
(i.e. pre-MMX) Pentium cores that have been enhanced with very wide
vector floating-point resources and ganged together to make the brains
of a flexible, x86-based GPU.
*Update: Intel contacted me to clarify that Gelsinger did not, in
fact, tell heise.de that Larrabee was based on P54C. This was
something that was apparently mangled in the Babelfish translation,
and Andreas at heise.de was pulling the P54C detail from some other
source. Nonetheless, I had already heard the information about the
Larrabee-Pentium-Pentagon connection from a source of my own, so I do
vouch for it.
You're probably wondering why Intel picked the old P54C to base
Larrabee off of, instead of, say, the later P55 part with MMX. The
reason, which Gelsinger did not reveal to heise.de and which comes
from a source of mine, is a bit surprising, in that it involves the
Pentagon.
Say "Pentagon Pentium" five times fast
Quite some time ago, after the Pentium was obsolete and Intel had
moved on, the company gave the RTL code for the processor to the
Pentagon so that the military could continue to fabricate a radiation
hardened version of it for use in military applications. Trailing-edge
hardware like the Pentium has the advantage of having been thoroughly
tested and debugged (cf. the P54C's infamous FDIV bug), and at the
time the military had its own fab facilities that could do some low-
volume fabrication. (I'm sure they still have such facilities for
prototyping.) So the Pentagon cleaned up the P54C's RTL code and began
producing a rad-hard version of the chip for military use.
A few years later, when the Pentagon had moved on from the P54C, they
offered the RTL back to Intel. So Intel took the core, which has a
very small footprint and by this time had been pretty thoroughly
debugged, and modified it for use in the many-core chip that later
became Larrabee.
Speaking of five times fast
While I'm just spilling all kinds of Larrabee beans, I might as well
drop another, performance-related tidbit that came my way. In an
upcoming SIGGRAPH paper, Intel will claim that Larrabee has 20x the
performance per watt of a Core 2 Duo and half the single-threaded
performance. It also has a 4MB coherent L2, and three-operand vector
instructions.
Note that I don't have any more context for the information I just
gave, so I'm not sure if "half the performance of Core 2 Duo" is a
clock-for-clock figure or not. If it is, recall that the Pentium's
pipeline is less than half the depth of Core 2's, so if the GPU does
debut in the 1.7GHz to 2.5GHz range, then that will help it in Core 2
comparisons. The other big unknown is the type of workload that Intel
is using for this ballpark performance figure. When it comes to in-
order (i.e., Larrabee) vs. out-of-order (i.e., Core 2) and short
pipeline vs. long pipeline, the type of workload involved makes all
the difference. So these few details that I've given tell you a lot
less than you might think at first; but something is better than
nothing—and nothing is what we have so far about Larrabee's
peformance.
http://arstechnica.com/news.ars/pos...-gpu-based-on-secret-pentagon-tech-sorta.html
Hmmm
If Intel is using old Pentium CPU technology in Larrabee, I hope they
also use old GPU tech for the rasterisation portions of the chip.
Specifically, Lockheed Martin Real3D graphics technology, which Intel
once owned the patents to, and probably still has knowledge of.