公开(公告)号：US3591787A

公开(公告)日：1971-07-06

申请号：US3591787D

申请日：1968-01-29

Applicant: IBM

Inventor： FREIMAN CHARLES V ,  WANG CHUNG CHIAN

IPC: G06F7/52 ,  G06F7/535 ,  G06F7/39 ,  G06F7/38

CPC classification number: G06F7/535 ,  G06F2207/5352

Abstract: A system and method for digital division employing a composite of table lookup and iteration techniques. A stored logic table is used which generates a factor M which when multiplied against the divisor, provides a new divisor in a predetermined range close to unity in value. Both the divisor and the dividend are then multiplied by the factor M, the capacity of the table lookup determining the maximum difference of the new divisor from unity. The arrangement is such that, depending upon the difference between the new divisor and unity, a selected number of new partial quotient digits is directly determined from a selected number of digits in newly generated partial remainders. By generating quotient digits in successive groups, only a few iterations are needed to divide one long number by another. Successive division steps entail merely the generation of new partial products, and derivation of the difference of these partial products from the previous partial remainder. By arranging the significant portion of the new divisor to be a negative quantity in a preferred form of system, only adder circuits need by employed. A high speed, high capacity binary digital division system utilizing these techniques is further arranged to utilize carry-save adder circuits to utilize carry and sum quantities without introducing carry propagation delays, and otherwise minimize operating cycle time.