Superconducting Technology Assessment - nitrd

LIMITATIONS OF
CURRENT TECHNOLOGY
Circuit Speeds Facing Limits
The government is observing increased difficulty as industry attempts to raise the processing performance of
today’s silicon-based supercomputer systems through improvements in circuit speeds. In the past several decades,
steady decreases in circuit feature sizes have translated into faster speeds and higher circuit densities that have
enabled ever-increasing performance. However, conventional technology has a limited remaining lifetime and is
facing increasing challenges in material science and power dissipation at smaller feature sizes.
There are already signs that the major commodity device industry is turning in other directions. The major microprocessor
companies are backing away from faster clock speeds and instead are fielding devices with multiple
processor “cores” on a single chip, with increased performance coming from architectural enhancements and
device parallelism rather than increased clock speed.
While the Semiconductor Industry Association (SIA) International Technology Roadmap for Semiconductors (ITRS)
projects silicon advances well into the next decade, large-scale digital processing improvements will almost certainly
come from increased parallelism, not raw speed.
Commercial and Government Interests Diverging
Over the past two decades, High-End Computing (HEC) systems have improved by leveraging a large commodity
microprocessor and consumer electronics base. However, future evolution of this base is projected to diverge from
the technology needs of HEC for national security applications by supporting more processors rather than faster
ones. The result will be limitations in architecture and programmability, for implementations of HEC based on the
traditional commodity technology base.
Power Requirements Swelling
For supercomputers, continuing reliance on this technology base means a continuation of the trend to massively
parallel systems with thousands of processors. However, at today's scale, the electrical power and cooling
requirements are bumping up against practical limits, even if ways were found to efficiently exploit the parallelism.
For example, the Japanese Earth Simulator system, which has been ranked number one on the list of the top 500
installed HEC, consumes approximately 6 megawatts of electrical power.
PANEL TASKED
A panel of experts from industry and academia, augmented by Agency subject matter experts, was assembled to
perform this study, bringing expertise from superconducting materials, circuitry, fabrication, high-performance
computer architecture, optical communications, and other related technologies. The panel:
02
■ Assessed RSFQ technology for application to high-performance computing systems available
after 2010, based on current projections of material science, device technology, circuit design,
manufacturability, and expected commercial availability of superconductive (SC) technology
over the balance of the decade.
■ Identified roadmaps for the development of the essential components, including microprocessor
circuits, memory, and interconnect, for high-end computer architectures by 2010.