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MINIMAL CORRECTION LOGIC FOR PARTIAL REMAINDER OVERFLOW IN A NON-RESTORING DIVIDE ALGORITHM

IP.com Disclosure Number: IPCOM000005568D
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-16

Publishing Venue

Motorola

Related People

Authors:
Doug MacGregor Mitchell Taylor James Kennedy

Abstract

The non-restoring divide algorithm is well known and has been used and understood for some time. Because this algorithm does not require that the partial remainder be recreated after an "over subtraction': it has fewer steps and as such can be implemented as a faster algorithm than the restoring divide operation which is common in microprocessors. A complete description of the algorithm is beyond the scope of this paper ISpanEl] but the basic concept is that when an "over subtraction" occurs, on the next iteration or iterations, it is possible to correct the partial remainder by keeping track of the results of the last operation and performing an add operation rather than a subtract. In this way the restore operation is not necessary. The non-restoring algorithm has the advantage of speed and the disadvantage that it requires increased control logic to select the type of operation to be performed.