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The Dadda multiplier is a hardware binary multiplier design invented by computer scientist Luigi Dadda in 1965. [1] It uses a selection of full and half adders to sum the partial products in stages (the Dadda tree or Dadda reduction ) until two numbers are left.
Multiply each bit of one of the arguments, by each bit of the other. Reduce the number of partial products to two by layers of full and half adders. Group the wires in two numbers, and add them with a conventional adder. [3] Compared to naively adding partial products with regular adders, the benefit of the Wallace tree is its faster speed.
In a fast multiplier, the partial-product reduction process usually contributes the most to the delay, power, and area of the multiplier. [7] For speed, the "reduce partial product" stages are typically implemented as a carry-save adder composed of compressors and the "compute final product" step is implemented as a fast adder (something faster ...
It is performed by reading the binary number from left to right, doubling if the next bit is zero, and doubling and adding one if the next bit is one. [5] In the example above, 11110011, the thought process would be: "one, three, seven, fifteen, thirty, sixty, one hundred twenty-one, two hundred forty-three", the same result as that obtained above.
A full adder can be viewed as a 3:2 lossy compressor: it sums three one-bit inputs and returns the result as a single two-bit number; that is, it maps 8 input values to 4 output values. (the term "compressor" instead of "counter" was introduced in [ 13 ] )Thus, for example, a binary input of 101 results in an output of 1 + 0 + 1 = 10 (decimal ...
A common example is the Data General Nova, which was a 16-bit design that performed 16-bit math as a series of four 4-bit operations. 4-bits was the word size of a widely available single-chip ALU and thus allowed for inexpensive implementation. Using the definition being applied to the 68000, the Nova would be a 4-bit computer, or 4/16.
Booth's algorithm examines adjacent pairs of bits of the 'N'-bit multiplier Y in signed two's complement representation, including an implicit bit below the least significant bit, y −1 = 0. For each bit y i, for i running from 0 to N − 1, the bits y i and y i−1 are considered.
Brickell [3] has published a similar algorithm that requires greater complexity in the electronics for each digit of the accumulator.. Montgomery multiplication is an alternative algorithm which processes the multiplier "backwards" (least significant digit first) and uses the least significant digit of the accumulator to control whether or not the modulus should be added.