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Superconductor electronics (SCE) promise computer systems with orders of magnitude higher speeds and lower energy consumption than their complementary metal–oxide semiconductor (CMOS) counterparts. At the same time, the scalability and resource utilization of superconducting systems are major concerns. Some of these concerns come from device-level challenges and the gap between SCE and CMOS technology nodes, and others come from the way Josephson junctions (JJs) are used. Toward this end, we notice that a considerable fraction of hardware resources are not involved in logic operations, but rather are used for fan-out and buffering purposes. In this article, we ask if there is a way to reduce these overheads, propose the use of JJs at the cell boundaries to increase the number of outputs that a single stage can drive, and establish a set of rules to discretize critical currents in a way that is conducive to this assignment. Finally, we explore the design trade-offs that the presented approach opens up and demonstrate its promise through detailed analog simulations and modeling analyses. Our experiments indicate that the introduced method leads to a 48% savings in the JJ count for a tree with a fan-out of 1024, as well as an average of 43% of the JJ count for signal splitting and 32% for clock splitting in ISCAS’85 benchmarks. 

When extremely low-energy processing is required, the choice of data representation makes a tremendous difference. Each representation (e.g., frequency domain, residue coded, and log-scale) embodies a different set of tradeoffs based on the algebraic operations that are either easy or hard to perform in that domain. We demonstrate the potential of a novel form of encoding, race logic, in which information is represented as the delay in the arrival of a signal. Under this encoding, the ways in which signal delays interact and interfere with one another define the operation of the system. Observations of the relative delays (for example, the outcome of races between signals) define the output of the computation. Interestingly, completely standard hardware logic elements can be repurposed to this end and the resulting embedded systems have the potential to be extremely energy efficient. To realize this potential in a practical design, we demonstrate two different approaches to the creation of programmable tree-based ensemble classifiers in an extended set of race logic primitives; we explore the trade-offs inherent to their operation across sensor, hardware architecture, and algorithm; and we compare the resulting designs against traditional state-of-the-art hardware techniques. 

Undergraduate research experiences are a promising way to broaden participation in computer architecture research and have been shown to improve student learning, engagement, and retention. These outcomes can be more profound and lasting if students experience research early. However, there are many barriers to early research in computer architecture some of which include the gap between pedagogy and research, the lower emphasis on hardware design compared to software in first-year courses, and the lack of online resources. We propose lowering these barriers through a methodical approach by involving undergraduates in early research and by creating freely available and innovative educational tools for designing hardware. We present the experience of a team of undergraduate students with research over one academic year using a Python hardware description language, PyRTL. PyRTL was developed to enable early entry into digital design. Its overarching goals are simplicity, usabil- ity, clarity, and extensibility, a stark contrast to traditional languages like Verilog and VHDL that have a steep learning curve. Instead of introducing traditional languages early in the undergraduate curriculum, PyRTL takes the opposite approach, which is to build on what students already know well: a popular programming language (Python), software design patterns, and software engineering principles. The students conducted their research in the context of the Early Research Scholars Program (ERSP), a program designed to expand access to research among women and underrepresented minority students in their second year through a well-designed support structure.