About unexpected realtime delay ...

No confuse. My logic was - despite function is loaded, if no pins are configured for read, then there is nothing to read.

P.S. I understand that linuxcnc is implemented how it is implemented. No complains.

Hal files are simple scrips they don't check if something is used or not, they just do what they are told, and halpins such as the parallel port input pins can be read and used by other things independent of the hal file.

By what things they can be read and used?

A custom M-code could use them without a hal file reference.
A python userspace component can look up the value of a hal pin.

Okay. Will check that. You gave me the point.

Thanks

Moved parport.X.read functions to servo thread and got stable 31000nS base period for two parports generating pulses for 5 joints at 32kHz.