Method and apparatus for performing two independent sum-of-absolute-difference (SAD) operations when receiving a single instruction (505, 705) is provided. The two operations may be performed in parallel. The operations process values stored in two source registers (405, 410) and the results are stored to a destination register (425). The source and destination registers each have two independently accessible sections, whereby a first SAD operation (401) can access a first section while a second independent SAD operation (402) can simultaneously access a second section of the register. The first SAD operation is performed on values in a first section of the source registers, the result being stored to a first section of the destination register. The second SAD operation is performed on values in a second section of the source registers, the result being stored to a second section of the destination register. The values may comprise pixel values.