Strange behaviour of a cyclic task with HZ = 1024

Hi, I have set the HZ constant to 1024 to increase the select resulution. But the results of my measurements are not as expected. I have a cyclical task (using select for timing) that inverts a parallel port bit in each cycle. I measure the high time with an oszillograph. Here are my results: 1

Behaviour of a cyclic task with HZ = 1024

Hi, I have set the HZ constant to 1024 to increase the select resulution. But the results of my measurements are not as expected. I have a cyclical task (using select for timing) that inverts a parallel port bit in each cycle. I measure the high time with an oszillograph. Here are my results: 1