ISSN ONLINE(23198753)PRINT(23476710)
Amazing porn model Belle Delphine nudes on sexelibre.org. Watch free video collection of Belle Delphine nede leaked
Rare Muslim porn and سكس on sexsaoy.com. Tons of Arab porn clips.
XNXX and Xvideos porn clips free on xnxxarabsex.com. Best XnXX porn tube channels, categorized sex videos, homemade and amateur porn.
Exlusive russian porn russiainporn.com. Get uniqe porn clips from Russia
Find out on sexjk.com best collection of Arabain and Hijab سكس
I. Hussain^{1}, R. K. Sah^{1}, M. kumar^{2}

Related article at Pubmed, Scholar Google 
Visit for more related articles at International Journal of Innovative Research in Science, Engineering and Technology
Multipliers are the basic building blocks of many VLSI computational units. The performance of such VLSI circuits depends on the performance of multipliers. Hence designing a high performance multiplier is a challenging task for VLSI designers. Wallace tree multiplier or Wallace multiplier is the most popular multiplier among the existing multipliers. Wallace multiplier is also known for its fast speed and low power consumption. Different techniques for designing a Wallace multiplier are available in the literature. In this paper, performance comparison review of various Wallace multiplier architectures is included.
Keywords 
Wallace multiplier, Reduced complexity, Power Dissipation, Delay. 
INTRODUCTION 
Digital signal processors are designed in such a way that it has a feature of DSP algorithm in real time. The basic building blocks of DSP are multiplier, arithmetic logic unit and multiply and accumulate unit. For real time applications the key issues in the design of computational building blocks of digital signal processor are speed and accuracy [1]. Multiplication is essential for computers, process controllers, microprocessors, digital signal processing and graphic engines. In DSP processor, multiplication is done by multiplier. So, system performance is determined by the performance of the multiplier. Hence various multiplier architectures have been proposed to increase the performance of the multiplier. 
There are different factors that drive for high performance electronic system design in terms of low power dissipation and high speed [23]. With the recent advances in technology, many researchers have worked on the design of increasingly more efficient multipliers. Main aim is to offer higher speed and lower power dissipation. This makes them compatible for various complex and portable VLSI circuit implementations. The block diagram of multiplier architecture is shown in Fig.1. The multiplier architecture consists of three parts: generation of partial product, addition of partial product and final addition. 
Fig.1.Block diagram of multiplier architecture 
Parallel multipliers are the high speed multiplier. There are so many multiplier architectures that are available for designing parallel multiplier. Wallace multiplier is one of them. A Wallace tree is an efficient hardware implementation of a digital circuit. It can multiply two integers. A multiplier based on Wallacetree structure is called Wallace multiplier. It is substantially faster than other multiplier [4]. 
In this paper, several types of Wallace multiplier architectures are studied that have reduced complexity, low power consumption and less latency as compared to the conventional Wallace multiplier. 
RELATED WORK 
CONVENTIONAL WALLACE MULTIPLIER 
A conventional Wallace multiplier is an efficient parallel multiplier. Wallace multiplier architecture has also three steps. In the first step, it generates partial product. If the multiplication is of NxN bits, then it produces N2 partial product. In accumulation of partial product, group of three adjacent rows are collected. Each group of three rows is reduced by using full adders and half adders. Full adders are used in each column where there are three bits whereas half adders are used in each column where there are two bits. If there is any single bit in any stage then it is passed to the next stage without any processing. The procedure of reduction is repeated unless two rows are obtained [4]. Fig. 2 shows 9bit conventional Wallace multiplier architecture [5]. This figure shows that the multiplication is achieved in three steps and the number of rows in the initial bit product array is nine. 
For an Nbit multiplier, the number of rows in the initial bit product array, r0, is N. The number of rows in subsequent stages of a conventional Wallace multiplier can be written as [5] 
Here, ri denotes the groups or stages, and ri mod 3 denotes the smallest non negative remainder of ri/3. The number of rows in subsequent stages of a conventional 9bit Wallace multiplier is calculated by using eqn.1. For a conventional 9bit Wallace multiplier, r0=N=9, r1=6, r2=4, r3=3, r4=2. 
Fig.2. 9bit Conventional Wallace multiplier 
REDUCED COMPLEXITY WALLACE MULTIPLIER 
Waters et al. presented the reduced complexity Wallace multiplier approach. Fig. 3[5] shows a reduced complexity Wallace multiplier. It is a modification to the second phase reduction method used in the conventional Wallace multiplier, in which number of the half adders is reduced. In the first phase, the partial product array is formed and it is converted in the form of an inverted pyramid array. An inverted pyramid array is formed when the bits in the left half of the partial product array is shifted in the upward direction. In the second phase, this array is divided into group of three rows each and full adders are used in each column. Half adders are used only when the number of reduction stages of the modified Wallace multiplier is exceeding that of the conventional Wallace multiplier. So this method reduces the number of half adders. 
In this modified Wallace multiplier, if (ri mod 3) = 0, then half adder is needed in the reduction stage; otherwise half adder is not required. The number of half adders in this architecture is equal to NS1, where N is the number of bits, and S is the number of stages. For 9bit multiplication using this Wallace multiplier architecture, only one half adder is used in the first and the second stage and two half adders are used in the final stage as shown in Fig. 3 [5]. Therefore, it is observed that the number of the reduction stages remain the same as compared to the conventional Wallace reduction whereas two more full adders and 17 fewer half adders are used in this modified Wallace multiplier in comparison with the conventional Wallace multiplier. 
Table 1[5] shows the comparison of complexity between the conventional Wallace multiplier and the reduced Wallace multiplier for sizes of 8, 16, 24, 32 and 64 bits. This table shows that using both multipliers yield the same number of the reduction stages, but the modified or reduced complexity Wallace multiplier has the advantage of reduced complexity in the number of gates. 
TABLE 1: COMPARISON OF COMPLEXITY 
NOVEL LOW POWER AND HIGH SPEED WALLACE MULTIPLIER 
A novel low power and high speed Wallace multiplier uses carry save addition algorithm to reduce the overall latency [6]. This leads to increased speed and reduced power dissipation. This is accomplished by the use of compressors in place of full adders, and the uses of Sklansky tree adder in place of the final carry propagate stage. The novel low power and high speed Wallace multiplier for RISC processors in shown in Fig.4 [6]. In the partial product reduction stage, if the number of adders used is decreased, it correspondingly reduces the latency in the Wallace tree multiplier. In this multiplier, two full adders having delay of four units are replaced by a single 4:2 compressor having latency of three units and 5:2 compressor having latency of four units replace three full adders having latency of six units. The use of the Sklansky adder in the structure further results in a reduced latency. 
Fig.4. Novel low power and high speed Wallace multiplier 
BOOTH RECODED WALLACE TREE MULTIPLIER 
Booth Recoded Wallace Tree Multiplier comprises of Booth recoding algorithm and compressor adders for its realization [7]. In this architecture, Booth Recoding algorithm is introduced to generate and reduce the number of the partial products of multiplier, whereas, 3:2, 4:2, and 5:2 compressor structures are introduced to reduce the number of partial product addition stages. In these compressors, critical delay path is minimized by replacing the XOR blocks with multiplexer blocks. Final two rows are summed using Carry Select Adder to produce the final result. This architecture has the advantage of higher speed and lower area. 
EFFICIENT HIGH SPEED WALLACE TREE MULTIPLIER 
In contrast to the conventional Wallace tree multiplier, an efficient high speed Wallace tree multiplier is composed of compressor adders and modified carry select adder [8]. In this architecture, 4:2 and 5:2 compressors are used for partial product reduction in the second stage whereas carry select adders are used to perform addition of two rows of bits in the final stage for reduction in carry propagation latency of the Wallace multiplier. 
An efficient high speed Wallace tree multiplier architecture has the advantage of reduced latency and reduced power consumption than the conventional Wallace multiplier. Table 2 [8] shows comparison of number of transistor and latency using 8bit Conventional Wallace Multiplier and 8bit Efficient High speed Wallace Tree Multiplier architectures. This table shows that the area is also reduced by using an efficient high speed Wallace tree multiplier in comparison with the conventional Wallace Multiplier because of the decrease in the number of transistors. 
Table 2. Comparison of number of transistor and latency 
WALLACE MULTIPLIER USING ENERGY EFFICIENT CMOS FULL ADDER 
Fig. 5 [9] shows the block diagram of Wallace multiplier architecture using energy efficient CMOS full adder. In this method modified reduced complexity Wallace Multiplier is designed with reduced power consumption and area by using energy efficient CMOS full adder in place of conventional full adder [9]. This multiplier architecture reduces power dissipation and also total number of gate counts is reduced. In this architecture, energy efficient CMOS full adder is used in place of conventional full adder. This reduces the overall power dissipation and also increases the speed. 
Fig.5. Wallace multiplier using Energy efficient CMOS full adder 
CONCLUSION 
In this paper, several types of Wallace multiplier architectures are studied and compared with the conventional Wallace multiplier architecture. It is observed that with reduced complexity and use of efficient adders, Wallace multiplier architecture gives better performance in terms of power, delay and area. 
References 
