  Energy-efficient real-time task scheduling has been actively explored in the
past decade. Different from the past work, this paper considers schedulability
conditions for stochastic real-time tasks. A schedulability condition is first
presented for frame-based stochastic real-time tasks, and several algorithms
are also examined to check the schedulability of a given strategy. An approach
is then proposed based on the schedulability condition to adapt a
continuous-speed-based method to a discrete-speed system. The approach is able
to stay as close as possible to the continuous-speed-based method, but still
guaranteeing the schedulability. It is shown by simulations that the energy
saving can be more than 20% for some system configurations
