Browse Prior Art Database

# Self Restoring Divide

IP.com Disclosure Number: IPCOM000092702D
Original Publication Date: 1967-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

IBM

Ross, RD: AUTHOR

## Abstract

During division, divisor A is placed in Reg A and dividend B is placed in Reg C. Reg BX is a right-hand extension of Reg 13 and provides a place in which the quotient bit is developed. The dividend field in Reg B is reduced towards zero by the value of divisor A. After each reduction, Regs B and BX are shifted left one po sition. Any quotient bit developed is inserted in the low-order position of Reg BX. Thus the original dividend placed in Regs B and BX is reduced to a remainder as it travels leftward in these Regs and the quotient correspondingly increases until it fills Reg BX.

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Self Restoring Divide

During division, divisor A is placed in Reg A and dividend B is placed in Reg
C. Reg BX is a right-hand extension of Reg 13 and provides a place in which the quotient bit is developed. The dividend field in Reg B is reduced towards zero by the value of divisor A. After each reduction, Regs B and BX are shifted left one po sition. Any quotient bit developed is inserted in the low-order position of Reg BX. Thus the original dividend placed in Regs B and BX is reduced to a remainder as it travels leftward in these Regs and the quotient correspondingly increases until it fills Reg BX.

A successful reduction occurs if the result of the reduction in the dividend field toward zero by the divisor has the same sign as the original dividend. An overdraw occurs if the result has the opposite sign to the original dividend. When an overdraw occurs, the dividend field is corrected, prior to shifting, by adding the divisor back to the dividend field. A shift is made, no quotient bit developed, and a reduction process is repeated until the full quotient is developed.

Reg A contains divisor A and Reg 13 contains the original dividend 13 or, during subsequent cycles, the then partial dividend. Reg C is connected to follow Reg 13. During the first part of the reduction cycle, the contents of Reg A are gated into Reg 13 to form the half-sums, i. e., A Exclusive-Or 13. Reg A and Reg C are connected to carry lookahead controls CLA which develops the carries to be...