Superconducting Technology Assessment - nitrd

6.5.2 POWER DISTRIBUTION AND CABLES – READINESS
Solution of the power distribution and cabling issues is technically feasible and fairly well understood at small-scale
applications. However, the design of high-current DC cabling for larger applications, (e.g., a petaflops supercomputer
where dimensions are in the order of several meters) remains to be done. For small systems, coaxial cabling has
been the primary choice for RF cabling. Designs and data for cabling at ~10 GB/s and up to ~1,000 signal lines are
available but must be developed further to support the many thousand RF lines required by a petaflops system.
Extension to support line rates of 40 GHz or higher has not been fully explored. The mode of operation may change
from microstrip/stripline to waveguides, which raises assembly and heat load issues. The good news is that, except
for HTS cabling and RF cabling beyond 20 Gb/s, the commercial cable manufacturing industry should be able to
support the needs of an RSFQ petaflops system with special order and custom products.
6.5.3 POWER DISTRIBUTION AND CABLES – PROJECTIONS
A projection of the current and projected state of suitable cabling for a petaflops RSFQ-based system is given
below. Until a full architecture is developed, it is not possible to quantify the electrical, thermal, line count, and
other requirements for the cabling.
TABLE 6-7. Current and Projected State of Suitable Cabling for Petaflops-scale System
Year 2004 2007
2009
DC Power Cables
—
—
—
Lines
Single Conductor
Flex Cable
Flex Cable
Max DC current/line
~ 1 Amp
~100 mA
~500 mA
RF Signal Cables
—
—
—
Line Count
~100
~1,000
~2,000
Data Rate Supported
10 Gb/s
20 Gb/s
20 Gb/s
Current Supply
Direct, Parallel
Direct, Serial
Switched or
Direct, Serial
6.5.4 POWER DISTRIBUTION AND CABLES – ISSUES AND CONCERNS
The operation at 50 GHz and beyond with acceptable bit error rates (BER) needs further development and testing,
including physical issues (such as conductive and dielectric material selection, dielectric losses) and electrical issues
(such as signaling types, drivers and receivers).
The combination of good electrical and poor thermal conductance is inherently difficult to meet since a good electrical
conductor is a good thermal conductor. The required density of I/O lines in large-scale systems is a factor of 10 greater
than the density achievable today (0.17 lines/mil) for flexible ribbon cables.
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