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ALU Operation for Addressing Arithmetic using Multiple Offset Sizes

IP.com Disclosure Number: IPCOM000038213D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-31

Publishing Venue

IBM

Related People

Authors:
Funk, MR Irish, JD Petrillo, RA Thomforde, DJ [+details]

Abstract

ALU operations are used for address arithmetic where address arithmetic supports multiple size offsets and tests to ensure that an invalid address was not generated. Described is a single 32-bit signed or unsigned displacement, although smaller displacements are implemented by placing a sign or zeroes to extend these smaller displacements. Further, the 32-bit displacement is used because its size corresponds to the largest offset. The ALU operation is defined as an effective address calculation where the low order 32 bits of the virtual address are binary-added to the 32 bits representing a displacement. The result is a 48-bit virtual address.