In this paper we investigate possible ways to improve the energy efficiency of a general purpose microprocessor. We show that the energy of a processor depends on its performance, so we chose the energy-delay product to compare different processors. To improve the energy-delay product we explore methods of reducing energy consumption that do not lead to performance loss (i.e. wasted energy), and explore methods to reduce delay by exploiting instruction level parallelism. We found that careful design reduced the energy dissipation by almost 25%. Pipelining can give approximately a 2/spl times/ improvement in energy-delay product. Superscalar issue, however, does not improve the energy-delay product any further since the overhead required offsets the gains in performance. Further improvements will be hard to come by since a large fraction of the energy (50-80%) is dissipated in the clock network and the on-chip memories. Thus, the efficiency of processors will depend more on the technology being used and the algorithm chosen by the programmer than the micro-architecture.

Energy dissipation in general purpose microprocessors

Portable devices demand low power consumption to prolong battery life. Gating the clock is one strategy for saving power. The authors' technique identifies self-loops in an FSM and uses the function described by the self-loops to gate the clock. Applying these techniques to standard benchmarks achieved an average 25% less power dissipation at a cost of only 5% more area. >

Saving power by synthesizing gated clocks for sequential circuits

This paper contains an evaluation of trends in the key system parameters (e.g., size, weight, function, performance, battery life) for battery-powered portable computers, together with a review of development trends in the technologies required for such systems. The discussion focuses on notebook-size portable computers. Those technologies which will have substantial impact on battery life and power budgets of future notebook computers receive the primary emphasis in this paper for example, liquid crystal displays, storage technology, wireless communication technology, and low power electronics. System power management is also be addressed. The basic theme of this paper is first to develop a view of what the key attributes of future notebook computers will be, and then to discuss how technologies must evolve to allow such systems to be advanced over the current state of the art in terms of portability and battery life. >

Technology directions for portable computers

A novel snubber-clamped diode-string ESD protection circuit for mixed voltage interface microprocessor applications is described. Analytical models, circuit simulation, electrical characterization, ESD electrothermal simulation, ESD test data, and an ESD analytical failure model are shown for shallow trench isolation (STI) and LOCOS CMOS technologies.

Analysis of snubber-clamped diode-string mixed voltage interface ESD protection network for advanced microprocessors

Optimization of a 3.3-V/ 5.0-V tolerant electrostatic discharge (ESD) protection network for both diffused n-well/LOCOS and retrograde well/shallow trench isolation (STI) CMOS technologies in a RISC microprocessor is discussed. ESD-related semiconductor-process key design features, ESD circuit operation, data, simulation and failure analysis are presented. ESD robustness of 4000-V human body model (HBM), 400-V machine model (MM), and 1500-V charge device model (CDM) is achieved in both technologies using a common design. >

Mixed-voltage interface ESD protection circuits for advanced microprocessors in shallow trench and LOCOS isolation CMOS technologies

This superscalar microprocessor is a 32b implementation of the PowerPC Architecture. With an estimated performance/power ratio of 25SPECint92/W at 80 MHz, this RISC style chip offers workstation-level performance packed into a low-power consumption, low-cost design ideal for notebooks and desktop computers. >

http://ieeexplore.ieee.org/iel2/1111/8026/00344665.pdf

R. Harris

Papers

A 3.0 W 75SPECint92 85SPECfp92 superscalar RISC microprocessor