A path metric difference computation unit is disclosed for computing path differences through a multiple-step trellis. The disclosed path metric difference computation unit computes differences between paths through a multiple-step trellis, wherein a first of the plurality of paths is a winning path for each single-step-trellis period of a multiple-step-trellis cycle, a second of the plurality of paths is a winning path for a first single-step-trellis period and is a losing path for a second single-step-trellis period of a multiple-step-trellis cycle and a third of the plurality of paths is a losing path for a first single-step-trellis period and is a winning path for a second single-step-trellis period of a multiple-step-trellis cycle. The disclosed path metric difference computation unit comprises one or more path metric difference generators for generating a path metric difference Δ0 for a second single-step-trellis period of the multiple-step-trellis cycle based on a difference between the first path and the second path, and a path metric difference Δ−1 for a first single-step-trellis period of the multiple-step-trellis cycle based on a difference between the first path and the third path, wherein one or more of intermediate path metric values and intermediate path metric difference values are reused to generate one or more of the path metric differences Δ0 and Δ−1.