A processor includes one or more processor cores configured to perform accumulate top (ACCT) and accumulate bottom (ACCB) instructions. To perform such instructions, at least one processor core of the processor includes an ACCT data path that adds a first portion of a block of data to a first lane of a set of lanes of a top accumulator and adds a carry-out bit to a second lane of the set of lanes of the top accumulator. Further, the at least one processor core includes an ACCB data path that adds a second portion of the block of data to a first lane of a set of lanes of a bottom accumulator and adds a carry-out bit to a second lane of the set of lanes of the bottom accumulator.