Dual-Clock SFQ Pipeline Architecture Without Path-Balancing DFFs
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Solution Overview
Problem
Current superconductor circuits require numerous path balancing D-Flip-Flops (DFFs) to ensure correct operation, leading to high component counts and increased chip area, which limits local clock frequency and peak throughput.
Innovation Solution
A new architecture employing fast and slow clock signals eliminates the need for path balancing DFFs, allowing SFQ logic gates to operate without them, while partial path balancing can be used to reduce throughput degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If path balancing DFFs are used to ensure correct operation, then circuit reliability is improved, but device complexity and chip area increase
Solution Approach 1:
The patent extracts and removes the path balancing DFFs from the SFQ circuit architecture. By using a new timing system with fast and slow clock signals, the circuit achieves correct operation without requiring these additional path balancing components, thus reducing device complexity while maintaining reliability
Solution Approach 2:
The patent changes the timing parameters by introducing dual clock frequencies (fast and slow clocks). This parameter change allows the circuit to operate correctly without path balancing DFFs by controlling signal propagation timing through the logic gates, thereby resolving the contradiction between reliability and device complexity
2Reliability
If path balancing DFFs are used to ensure correct operation, then circuit reliability is improved, but chip area increases
Solution Approach 1:
The patent removes path balancing DFFs from the circuit architecture, directly reducing the chip area occupied by these components. The new dual-clock timing system achieves the same reliability function with significantly less area by using temporal control instead of additional hardware
Solution Approach 2:
The patent uses signal replication through the dual-clock system where inputs are presented multiple times at different timing phases. This temporal copying approach replaces the need for spatial replication of path balancing DFFs, reducing chip area while maintaining operational correctness
3Device complexity
If component count is reduced by eliminating path balancing DFFs, then device complexity is reduced, but peak throughput may degrade
Solution Approach 1:
The patent introduces dynamic timing control with two different clock frequencies. The fast clock drives the logic gates for high-speed operation, while the slow clock controls input presentation and output collection. This dynamic timing approach allows the simplified circuit to maintain peak throughput by optimizing signal propagation timing without requiring path balancing DFFs
Solution Approach 2:
The patent uses periodic action through the dual-clock system where inputs are presented periodically at the slow clock rate and logic operations occur at the fast clock rate. This periodic timing structure ensures that signals propagate through the reduced component circuit correctly while maintaining high peak throughput during the fast clock phases
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in significant reductions in Josephson junction count and chip area, allowing for increased local clock frequency and flexible trade-offs between path balancing overhead and peak throughput.
Implementation Method 1
Availability of Josephson junctions which can serve as picosecond two-terminal devices. Moreover, these junctions can be impedance-matched with the superconducting microstrip lines, ensuring the ballistic transfer of generated waveforms along lines
Implementation Method 2
Availability of superconducting microstrip transmission lines capable of transferring picosecond waveforms over virtually any interchip distances with speed approaching half of that of light, and with low attenuation and dispersion
Data Source
AI summary
An SFQ circuit system includes at least one SFQ block having a plurality of SFQ logic gates. Characteristically, at least a portion of the SFQ logic gates are arranged in series. The SFQ circuit system includes a timing system configured to provide a first set of inputs and collect a first set of outputs of the at least one SFQ block at a rate defined by a slow clock frequency while the SFQ logic gates are clocked at a fast clock frequency. Advantageously, the rate is sufficiently slow to allow the first set of inputs to propagate through all levels of the SFQ logic gates to produce the first set of outputs of the at least one SFQ block without colliding with a second set of inputs to the at least one SFQ block.