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.