Power dissipation and thermal issues are increasingly significant in modern processors. As a result, it is crucial that power/performance tradeoffs be made more visible to chip architects and even compiler writers, in addition to circuit designers. Most existing power analysis tools achieve high accuracy by calculating power estimates for designs only after layout or floorplanning are complete. In addition to being available only late in the design process, such tools are often quite slow, which compounds the difficulty of running them for a large space of design possibilities.This paper presents Wattch, a framework for analyzing and optimizing microprocessor power dissipation at the architecture-level. Wattch is 1000X or more faster than existing layout-level power tools, and yet maintains accuracy within 10% of their estimates as verified using industry tools on leading-edge designs. This paper presents several validations of Wattch's accuracy. In addition, we present three examples that demonstrate how architects or compiler writers might use Wattch to evaluate power consumption in their design process.We see Wattch as a complement to existing lower-level tools; it allows architects to explore and cull the design space early on, using faster, higher-level tools. It also opens up the field of power-efficient computing to a wider range of researchers by providing a power evaluation methodology within the portable and familiar SimpleScalar framework.

Wattch: a framework for architectural-level power analysis and optimizations

The conventional digital hardware computational blocks with different structures are designed to compute the precise results of the assigned calculations. The main contribution of our proposed Bio-inspired Imprecise Computational blocks (BICs) is that they are designed to provide an applicable estimation of the result instead of its precise value at a lower cost. These novel structures are more efficient in terms of area, speed, and power consumption with respect to their precise rivals. Complete descriptions of sample BIC adder and multiplier structures as well as their error behaviors and synthesis results are introduced in this paper. It is then shown that these BIC structures can be exploited to efficiently implement a three-layer face recognition neural network and the hardware defuzzification block of a fuzzy processor.

Bio-Inspired Imprecise Computational Blocks for Efficient VLSI Implementation of Soft-Computing Applications

A performance analysis of 1-bit full-adder cell is presented. The adder cell is anatomized into smaller modules. The modules are studied and evaluated extensively. Several designs of each of them are developed, prototyped, simulated and analyzed. Twenty different 1-bit full-adder cells are constructed (most of them are novel circuits) by connecting combinations of different designs of these modules. Each of these cells exhibits different power consumption, speed, area, and driving capability figures. Two realistic circuit structures that include adder cells are used for simulation. A library of full-adder cells is developed and presented to the circuit designers to pick the full-adder cell that satisfies their specific applications.

Performance analysis of low-power 1-bit CMOS full adder cells

This book provides an up-to-date account of RNSs and arithmetic. It covers the underlying mathematical concepts of RNSs; the conversion between conventional number systems and RNSs; the implementation of arithmetic operations; various related applications are also introduced. In addition, numerous detailed examples and analysis of different implementations are provided.

Residue Number Systems: Theory and Implementation

We present a new design for a 1-b full adder featuring hybrid-CMOS design style. The quest to achieve a good-drivability, noise-robustness, and low-energy operations for deep submicrometer guided our research to explore hybrid-CMOS style design. Hybrid-CMOS design style utilizes various CMOS logic style circuits to build new full adders with desired performance. This provides the designer a higher degree of design freedom to target a wide range of applications, thus significantly reducing design efforts. We also classify hybrid-CMOS full adders into three broad categories based upon their structure. Using this categorization, many full-adder designs can be conceived. We will present a new full-adder design belonging to one of the proposed categories. The new full adder is based on a novel xor-xnor circuit that generates xor and xnor full-swing outputs simultaneously. This circuit outperforms its counterparts showing 5%-37% improvement in the power-delay product (PDP). A novel hybrid-CMOS output stage that exploits the simultaneous xor-xnor signals is also proposed. This output stage provides good driving capability enabling cascading of adders without the need of buffer insertion between cascaded stages. There is approximately a 40% reduction in PDP when compared to its best counterpart. During our experimentations, we found out that many of the previously reported adders suffered from the problems of low swing and high noise when operated at low supply voltages. The proposed full adder is energy efficient and outperforms several standard full adders without trading off driving capability and reliability. The new full-adder circuit successfully operates at low voltages with excellent signal integrity and driving capability. To evaluate the performance of the new full adder in a real circuit, we embedded it in a 4- and 8-b, 4-operand carry-save array adder with final carry-propagate adder. The new adder displayed better performance as compared to the standard full adders

/pdf/design-of-robust-energy-efficient-full-adders-for-deep-5ba51kaofh.pdf

Design of Robust, Energy-Efficient Full Adders for Deep-Submicrometer Design Using Hybrid-CMOS Logic Style

Recently reported logic style comparisons based on full-adder circuits claimed complementary pass-transistor logic (CPL) to be much more power-efficient than complementary CMOS. However, new comparisons performed on more efficient CMOS circuit realizations and a wider range of different logic cells, as well as the use of realistic circuit arrangements demonstrate CMOS to be superior to CPL in most cases with respect to speed, area, power dissipation, and power-delay products. An implemented 32-b adder using complementary CMOS has a power-delay product of less than half that of the CPL version. Robustness with respect to voltage scaling and transistor sizing, as well as generality and ease-of-use, are additional advantages of CMOS logic gates, especially when cell-based design and logic synthesis are targeted. This paper shows that complementary CMOS is the logic style of choice for the implementation of arbitrary combinational circuits if low voltage, low power, and small power-delay products are of concern.

/pdf/low-power-logic-styles-cmos-versus-pass-transistor-logic-40lwlx0imm.pdf

Low-power logic styles: CMOS versus pass-transistor logic

New VLSI circuit architectures for addition and multiplication modulo (2/sup n/-1) and (2/sup n/+1) are proposed that allow the implementation of highly efficient combinational and pipelined circuits for modular arithmetic. It is shown that the parallel-prefix adder architecture is well suited to realize fast end-around-carry adders used for modulo addition. Existing modulo multiplier architectures are improved for higher speed and regularity. These allow the use of common multiplier speed-up techniques like Wallace-tree addition and Booth recoding, resulting in the fastest known modulo multipliers. Finally, a high-performance modulo multiplier-adder for the IDEA block cipher is presented. The resulting circuits are compared qualitatively and quantitatively, i.e., in a standard-cell technology, with existing solutions and ordinary integer adders and multipliers.

Efficient VLSI implementation of modulo (2/sup n//spl plusmn/1) addition and multiplication

The addition of two binary numbers is the fundamental and most often used arithmetic operation on microprocessors, digital signal processors (DSP), and data-processing application-specific integrated circuits (ASIC). Therefore, bi¬ nary adders are crucial building blocks in very large-scale integrated (VLSI) circuits. Their efficient implementation is not trivial because a costly carrypropagation operation involving all operand bits has to be performed. Many different circuit architectures for binary addition have been proposed over the last decades, covering a wide range of performance characteristics. Also, their realization at the transistor level for full-custom circuit implemen¬ tations has been addressed intensively. However, the suitability of adder archi¬ tectures for cell-based design and hardware synthesis both prerequisites for the ever increasing productivity in ASIC design — was hardly investigated. Based on the various speed-up schemes for binary addition, a compre¬ hensive overview and a qualitative evaluation of the different existing adder architectures are given in this thesis. In addition, a new multilevel carryincrement adder architecture is proposed. It is found that the ripple-carry, the carry-lookahead, and the proposed carry-increment adders show the best overall performance characteristics for cell-based design. These three adder architectures, which together cover the entire range of possible area vs. delay trade-offs, are comprised in the more general prefix adder architecture reported in the literature. It is shown that this universal and flexible prefix adder structure also allows the realization of various customized adders and of adders fulfilling arbitrary timing and area constraints. A non-heuristic algorithm for the synthesis and optimization of prefix adders is proposed. It allows the runtime-efficient generation of area-optimal adders for given timing constraints.

Binary adder architectures for cell-based VLSI and their synthesis

A VLSI implementation of the International Data Encryption Algorithm is presented. Security considerations led to novel system concepts in chip design including protection of sensitive information and on-line failure detection capabilities. BIST was instrumental for reconciling contradicting requirements of VLSI testability and cryptographic security. The VLSI chip implements data encryption and decryption in a single hardware unit. All important standardized modes of operation of block ciphers, such as ECB, CBC, CFB, OFB, and MAC, are supported. In addition, new modes are proposed and implemented to fully exploit the algorithm's inherent parallelism. With a system clock frequency of 25 MHz the device permits a data conversion rate of more than 177 Mb/s. Therefore, the chip can be applied to on-line encryption in high-speed networking protocols like ATM or FDDI. >

R. Zimmermann

Papers

Low-power logic styles: CMOS versus pass-transistor logic

Efficient VLSI implementation of modulo (2/sup n//spl plusmn/1) addition and multiplication

Binary adder architectures for cell-based VLSI and their synthesis

A 177 Mb/s VLSI implementation of the International Data Encryption Algorithm

Computer Arithmetic: Principles, Architectures, and VLSI Design