David Chinnery

Minimization of dynamic and static power through joint assignment of threshold voltages and sizing optimization

We describe an optimization strategy for minimizing total power consumption using dual threshold voltage (Vth) technology. Significant power savings are possible by simultaneous assignment of Vth with gate sizing. We propose an efficient algorithm based on linear programming that jointly performs Vth assignment and gate sizing to minimize total power under delay constraints. First, linear programming assigns the optimal amounts of slack to gates based on power-delay sensitivity. Then, an optimal gate configuration, in terms of Vth and transistor sizes, is selected by an exhaustive local search. Benchmark results for the algorithm show 32% reduction in power consumption on average, compared to sizing only power minimization. There is up to a 57% reduction for some circuits. The flow can be extended to dual supply voltage libraries to yield further power savings.

Closing the power gap between ASIC and custom: an ASIC perspective

We investigate differences in power between application-specific integrated circuits (ASICs) and custom integrated circuits, with examples from 0.6/spl mu/m to 0.13/spl mu/m CMOS. A variety of factors cause synthesizable designs to consume /spl times/3 to /spl times/7 more power. We discuss the shortcomings of typical synthesis flows, and changes to tools and standard cell libraries needed to reduce power. Using these methods, we believe that the power gap between ASICs and custom circuits can be closed to within /spl times/2.

A functional validation technique: biased-random simulation guided by observability-based coverage

We present a simulation-based semi-formal verification method for sequential circuits described at the register-transfer level. The method consists of an iterative loop where coverage analysis guides input pattern generation. An observability-based coverage metric is used to identify portions of the circuit not exercised by simulation. A heuristic algorithm then selects probability distributions for biased random input pattern generation that targets non-covered portions. This algorithm is based on an approximate analysis of the circuit modeled as a Markov chain at steady state. Node controllability and observability are estimated using a limited depth reconvergence analysis and an implicit algorithm for manipulating probability distributions and determining steady-state behavior. An optimization algorithm iteratively perturbs the probability distributions of the primary inputs in order to improve estimated coverage. The coverage enhancement achieved by our approach is demonstrated on benchmarks from the ISCAS89 and VIS suites.

Linear programming for sizing, V th and V dd assignment

Most circuit sizing tools calculate the tradeoff between each gates delay and power or area, and then greedily change the gate with the best tradeoff. We show this is suboptimal. Instead we use a linear program to minimize circuit power. The linear program provides a fast and simultaneous analysis of how each gate affects gates it has a path to. Our approach reduces power by up to 30% compared to commercial software, with a 0.13um library. The runtime for posing and solving the linear program scales linearly with circuit size

Low power multiplication algorithm for switching activity reduction through operand decomposition

A novel low power multiplication algorithm for reducing switching activity through operand decomposition is proposed. Our experimental results show 12% to 18% reduction in logic transitions in both array multipliers and tree multipliers of 32 bits and 64 bits. Similar results are obtained for dynamic power dissipation after logic synthesis. One additional logic gate is required on the critical path for operand decomposition, which corresponds to only an additional 2% to 6% of total delay in these four cases. Thus, the proposed algorithm can be applied to many digital systems where power consumption is a major design constraint.

Closing the Power Gap Between ASIC & Custom

Explainshow to use low power design in an automated design flow, and examine the design time and performance trade-offs Includes the latest tools and techniques for low power design applied in an ASIC design flow Focuses on low power in an automated design methodology, a much neglected area

Achieving 550 MHz in an ASIC methodology

Typically, good automated ASIC designs may be two to five times slower than handcrafted custom designs. At last years DAC this was examined and causes of the speed gap between custom circuits and ASICs were identified. In particular, faster custom speeds are achieved by a combination of factors: good architecture with well-balanced pipelines; compact logic design; timing overhead minimization; careful floorplanning, partitioning and placement; dynamic logic; post-layout transistor and wire sizing; and speed binning of chips. Closing the speed gap requires improving these same factors in ASICs, as far as possible. In this paper we examine a practical example of how these factors may be improved in ASICs. In particular we show how techniques commonly found in custom design were applied to design a high-speed 550 MHz disk drive read channel in an ASIC design flow.

Automatic Replacement of Flip-Flops by Latches in ASICs

We have overcome some of the limitations of existing ASIC tools for handling latch-based designs, providing a theoretically valid and working methodology for retiming latches by retiming flip-flops. We have demonstrated a successful approach to replacing flip-flops on critical paths by latches to speed up ASICs, providing actual speed improvements of 5% to 20% on real commercial designs.

Linear programming for sizing, V/sub th/ and V/sub dd/ assignment

Most circuit sizing tools calculate the tradeoff between each gates delay and power or area, and then greedily change the gate with the best tradeoff. We show this is suboptimal. Instead we use a linear program to minimize circuit power. The linear program provides a fast and simultaneous analysis of how each gate affects gates it has a path to. Our approach reduces power by up to 30% compared to commercial software, with a 0.13/spl mu/m library. The runtime for posing and solving the linear program scales linearly with circuit size.