Abstract: Low-energy computing is an idea whose time has come. Applications include the smallest systems (where battery size and weight are crucial) as well as the largest systems (where power supply and cooling are crucial). To turn an F E T on or off requires transferring a certain amount of energy (the switching energy). The energy dissipated during this transfer need not be related to the energy transferred, but in ordinary CMOS logic circuits both quantities are on the order of $CV,2,, where C is the capacitance of a typical node, and V d d is the operating voltage. This level of dissipation is unavoidable if a l l the needed electrons are extracted from the V d d terminal of the power supply and ret,urned to the ground terminal. The essential idea of adiabatic computing is to construct circuits that allow each needed electron to be extracted at the lowest feasible voltage and returned at the highest feasible voltage. Ramp-like power/clock signals are required. Obviously it is advantageous to reduce c and V d d , but there are limits; in any case for the purposes of this paper we take such reductions for granted and show how dissipation can be further reduced at any particular V d d and c. The theoretical limit on dissipation is 0 for logically reversible operations, and kT for logically irreversible operations (1). Since kT is six or seven orders of magnitude below present-day values of $CV2d, there is considerable room for compromise. The logic family considered here, which we call 2N-2N2D, emphasizes overall system feasibility and throughput, while providing energy savings of “only” half an order of magnitude or so. Unlike previous diode-based energy recovery schemes (2; 3; 4) our major design goal was to present a nearly constant, data-independent capacitive load to the clock even though it makes 2N-2N2D about twice as complex as 1T1D (4). Constant load is vital, permitting operation from “stored energy” clock drivers. We have detailed simulations of such a clock driving a 6000-bit 2N-2N2D shift register ring, recovering over 75% of the transferred energy.