  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) 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 gate cascading and
consider continuous or pulsed SW generation scenarios. 31nW is the maximum
transducer power consumption for which a 32-bit BKA SW implementation can
outperform its 7nm CMOS counterpart.
