Abstract
In the early stages of a novel technology development, it is difficult
to provide a comprehensive assessment of its potential capabilities and
impact. Nevertheless, some preliminary estimates can be drawn and are
certainly of great interest and in this paper we follow this line of
reasoning within the framework of the Spin Wave (SW) based computing
paradigm. In particular, we are interested in assessing the
technological development horizon that needs to be reached in order to
unleash the full SW paradigm potential such that SW circuits can
outperform CMOS counterparts in terms of energy consumption. In view of
the zero power SWs propagation through ferromagnetic waveguides, the
overall SW circuit power consumption is determined by the one associated
to SWs generation and sensing by means of transducers. While current
antenna based transducers are clearly power hungry recent developments
indicate that magneto-electric (ME) cells have a great potential for
ultra-low power SW generation and sensing. Given that MEs have been only
proposed at the conceptual level and no actual experimental
demonstration has been reported we cannot evaluate the impact of their
utilization on the SW circuit energy consumption. However, we can
perform a reverse engineering alike analysis to determine ME delay and
power consumption upper bounds that can place SW circuits in the leading
position. To this end, we utilize a 32-bit Brent-Kung Adder (BKA) as
discussion vehicle and compute the maximum ME delay and power
consumption that could potentially enable a SW implementation able to
outperform its 7nm CMOS counterpart. We evaluate different BKA SW
implementations that rely on conversion- or normalization-based gate
cascading and consider continuous or pulsed SW generation scenarios. Our
evaluations indicate that 31nW is the maximum transducer power
consumption for which a 32-bit Brent-Kung SW implementation can
outperform its 7nm CMOS counterpart in terms of energy consumption.