creating iir digital filter with DSP Builder

I use FDATool created a 8 order low-pass butterworth filter model, the sampling frequency is 80 kHz, the cut-off frequency is533 Hz, this model meet the need to output, but according to the model to build the same function model with DSP Builder, the result of the DSP Builder model is not consistent with the FDATool model, the parameters and module function in DSP Builder model using are consistent with FDATool, please give the solutions, what is caused the problem? Thanks a lot.