Reconfigurable latch controllers for low power asynchronous circuits

Abstract

A method for reducing the power consumption in asynchronous micropipeline-based circuits is presented. The method is based around a new design for latch controllers in which the operating mode of the pipeline latches (normally open/transparent or normally closed/opaque) can be selected according to the dynamic processing demand on the circuit. Operating in normally-closed mode prevents spurious transitions from propagating along a static pipeline, at the expense of reduced throughput. Tests of the new latch controller circuits on a pipelined multiplier datapath show that reductions in energy per operation of up to 32% can be obtained by changing to the normally-closed operating mode. Estimates suggest that in a typical application which exhibits a variable processing demand, a power reduction of between 16-24% is possible, with little or no impact on maximum throughput.

Adaptive pipeline structures for speculation control

“…So it is not surprising that there is a great variety of latch controller types that can be built. This section considers the set of four-phase (return to zero) controllers implementing protocols used in AMULET3 [8].…”

“…For each of the above protocols there can be two variations depending on when the latches become transparent [8]:…”

“…Thus normally-closed latch controllers lead to more energy efficient pipelines, while normally-open controllers lead to faster pipelines. To enable this trade off at run-time, reconfigurable latch controllers that can be either normally-open or closed have already been developed [8] and are incorporated in the design of AMULET3.…”

“…The reconfigurable normally open/closed operating mode [8], is an attractive feature, so it is retained in the proposed latch controllers. The next section defines two (collapsible) latch controllers (for the broad and broadish protocols) that are configurable as collapsed or normal and as normally open or closed.…”

“…They are based on the existing latch controllers by Lewis et al [8]. broadish protocol ( figure 6 shows the existing controller).…”