Title:
|
Architecture Level Power-Performance Trade-ofts in Data-dominated Designs
|
As the demand for feature-rich portable devices continues to increase, new techniques are
needed to minimise power consumption. This thesis is concerned with the development and
validation of new systematic architectural methods of determining pipeline stage insertion in
data-dominated designs with the aim of reducing dynamic power consumption. The methods
place special emphasis on the number of latches used in pipeline stages and voltage scaling.
The first part of the thesis addresses power:minimisation through systematic analysis of the
number of latches in pipeline stages. A new pipeline stage insertion (PSI) method operating
at the architectural level is developed which takes into account system clock period and FEs
outputs and delays. A PSI algorithm based on analytical heuristic equations is formulated to
ensure the successful application of this method to any given data-dominated design. The
input to the algorithm 'is designer clock period and naively inserted pipeline stages. The
output from the algorithm is a pipelined design fulfilling the timing constraint with the least
dynamic power consumption. To support efficient power-performance trade-offs
exploration, the algorithm was fully automated.
The second part of the thesis focuses on the validation of the PSI method using two real-life
case studies: triple data path floating-point adder· and MPEG-I motion compensation
module. These designs are common in many portable devices and have numerous
implementation challe·nges including large number of FEs and significant power
consumption. Extensive experimental results show that for the motion compensation
module, the PSI is able to reduce dynamic power consumption by up to 30% compared with
other reported approaches.
The final part of the thesis concentrates on voltage scaling (VS) and its impact on pipeline
stages. The timing slack available in each stage is investigated, with the aim of further
reducing power consumption by lowering the supply voltage. The PSI method is modified to
support voltage scaling, and as a result, a new pipeline stage insertion with voltage scaling
(PSI-VS) method is proposed. Experimental results show that the PSI-VS can lead to
significant power saving compared with PSI without VS. For the MPEG-I motion
compensation case study, a power saving of 68% is observed. All the developed methods
have linear time complexity as the number of pipeline stages increases, facilitating their
application to large designs without incurring run time penalty. The results for the case
studies were based on a synthesisable RTL implementation using 90nrn technology together
with accurate power analysis using commercial tools.
|