Thermal Impacts on NoC Interconnects

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Thermal Impacts on NoC Interconnects

• Sheng Xu, Ibis Benito, Wayne Burleson
• VLSI Circuits and Systems Group
• University of Massachusetts Amherst

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Thermal Issues in NoCs

• Thermal issues are an increasing concern in
  microelectronics
• Increased power density
• The increasing vulnerability of the system due
  to temperature effects in terms of delay,
  leakage, reliability
• Technology Scaling Result
• Temperature effects become more significant
• Designing for performance becomes more
  difficult as the technology scales
• Need to understand the impact of thermal
  variations for hotspot reduction

Sketch of a possible thermal profile on a 3x3
network-on-chip
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Device and Interconnect Modeling

• Two Interconnect circuits are analyzed

• Repeater Insertion Line
• Differential Current Sensing

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Temporal Thermal Variation on DCS vs Repeated
Interconnect
Percentage of delay increase for temporal thermal
variation on a 3mm repeated wire.
Comparison between the impact on delay and energy
due to temporal thermal variation on a repeated
interconnect and differential current sensing for
a 45nm, 3mm wire.
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Modeling Spatial Thermal Variation on
Interconnect Circuit

• 3mm interconnect
• Temperature gradients from 10C to 50C
• Lowest temperature is swept from 30C to 60C in
  both directions

Spatial distribution profiles applied to a
repeated interconnect and a current-sensed
interconnect.
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Spatial Thermal Variation on DCS vs Repeated
Interconnect
Impact of two nonuniform thermal distribution
profiles on the delay of 65nm, 45nm and 32nm DCS.
Comparison between the impact on delay and energy
due to spatial thermal variation on a repeated
interconnect and differential current sensing.
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Summary

• Repeater insertion and DCS techniques have been
  implemented and compared in the presence of
  different thermal profiles for 65nm, 45nm and
  32nm technologies
• A decreasing spatial temperature impacted
  performance more than an increasing profile
• Delay degradation of an alternative differential
  current sensing (DCS) technique is largely
  determined by the amplifier temperature
• Shorter wires in NoCs will be preferable from a
  thermal standpoint.
• Design for balanced core temperatures becomes
  extremely important
• An alternative solution such as DCS may result in
  better performance from a thermal standpoint