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Godiva chip. Benchmark tests confirm it works as its designers intended . |
ISI has completed StreamAdd benchmarking, which measures memory bandwidth, on
a single Godiva chip running as part of the Long's Peak system.
The result: the measured throughput of the Godiva chip and the original-equipment
Itanium chip is roughly the same. "But our chip uses only one hundredth the electrical
power of the Itanium," noted Draper.
Like other PIM chips, Godiva is an effort to minimize the communication bottleneck
that takes place when processing chips have to go back and forth to separate memory
chips to get data for computations, and then store the results. "The theory,"
said Draper, "is that a PIM chip can keep results and data in its own memory,
resulting in dramatic gains in speed. We now see these results in actual benchmarking."
The system was benchmarked with only a single Godiva chip in place. But Hall
notes that the chip was designed to be used in eight-chip configurations. "The
bottom line is we will deliver eight times the computing power using less than
one tenth of the electricity."
The mismatch goes farther. Because the Godiva effort was a proof-of-concept
academic research project, the Godiva team used a relatively slow clock rate —
one-sixth the rate of the Itanium.
"A commercial implementation could operate at a state-of-the-art clock rate,"
said Hall, who added that benchmarking was continuing in other standard measures
of performance.
"But we believe that for certain uses that demand high memory bandwidth, such
as multimedia, complex scientific modeling and database access, and knowledge
discovery, the existing Godiva chip will deliver at least the order-of-magnitude
performance improvement that our initial design was aimed at achieving, and likely
significantly more."
The 56-million transistor Godiva chip improves on an earlier PIM chip created
in a previous ISI project called DIVA. Godiva added address translation and eight
single-precision floating point units, and contains a memory interface compatible
with DDR SDRAM memory buses.
One of the largest chips ever realized in academia, Godiva was fabricated at
Taiwan Semiconductor Manufacturing Corporation (TSMC) through ISI's MOSIS chip
brokerage
Besides Hall and Draper, the Godiva team includes ISI researchers Jacqueline
Chame (Compiler and Application Benchmarking), Tim Barrett (System Integration),
Jeff Sondeen (VLSI), Dale Chase (System Integration), Spundun Bhatt (Compiler
and System Software), and many ISI graduate students.
Defense agencies including DARPA and the Air Force Research Laboratory (AFRL)
funded the project.