A data processing apparatus that converts a plurality of signed digits representing an input value in redundant representation comprises receiver circuitry to receive, at each of a plurality of iterations, a signed digit from the plurality of signed digits, and previous intermediate data from a previous iteration. Concatenation circuitry performs a concatenation of bits corresponding to the signed digit and bits of the previous intermediate data to produce updated intermediate data. Output circuitry provides the updated intermediate data as previous intermediate data of a next iteration. The previous intermediate data comprises S3[i] in non-redundant representation, which is at least part of the input value multiplied by 3 in non-redundant representation.

A processing apparatus has combined divide-square root circuitry for performing a radix-N SRT divide algorithm and a radix-N SRT square root algorithm, where N is an integer power-of-2. The combined circuitry has shared remainder updating circuitry which performs remainder updates for a greater number of iterations per cycle for the SRT divide algorithm than for the SRT square root algorithm. This allows reduced circuit area while avoiding the SRT square root algorithm compromising the performance of the SRT divide algorithm.