Browse Prior Art Database

Table Lookup Multiplication

IP.com Disclosure Number: IPCOM000097035D
Original Publication Date: 1962-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Blaauw, GA: AUTHOR [+4]

Abstract

Multiplication is performed by first referencing a table stored in the main memory to develop partial products and then adding the partial products to an accumulation of partial products to develop the final product.

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Table Lookup Multiplication

Multiplication is performed by first referencing a table stored in the main memory to develop partial products and then adding the partial products to an accumulation of partial products to develop the final product.

Memory has a multiplication table which is addressable according to digits of the multiplier (MP) and multiplicant (MC). Location, e.g., XX72 holds 14: location XX69 holds 54. The MP and MC digits are available at MP and MC registers. The presently effective MP and MC digits are presented to memory address register MAR as tens and units digits of the table address. A fixed address device, which provides the higher order digits of the address, locates the table in memory.

The table, e.g., may be located at memory addresses 1000 to 1099; each location holding a two-digit partial product. Assume the problem is 5 x 7. The fixed address device provides the two high-order digits 10, the MP register provides the tens digit 5 and the MC register provides the units digit 7. The fixed address, the MP and MC digits combine to form table address 1057 in MAR. Location 1057 holds the product of 5 x 7 or 35. MAR references location 1057 to read out the 35 from memory to MDR.

The first partial product in MDR passes through an adder to an accumulator. Subsequent partial products, referenced from the table to MDR, are combined with the accumulation of partial products in the accumulator via the adder, utilizing the feedback path from accumu...