AD5933 Time taken for measurement

Hi

I'm using the AD5933 Eval board to measure capacitances in the range 100pF to 2000pf, with MCLK = 1MHz and sampling frequency at fixed at 1KHz. 

The Eval board takes considerably longer to do a measurement compared to when the MCLK is at 16MHz. I'm not sure if its something inherent to the AD5933 or it is to do with how the eval board and the software are designed.

A single measurement with 200 frequency points would take upwards of 20 seconds to finish. Sometimes exceeding 30 seconds.

Does anyone know if this is to be expected or if there's a solution? 

Thanks in advance