Max Step frequency from EMC

What would be the expected max Parallel portfrequency of EMC on a
1GHz Athlon in stepper mode?

At the bottom of this page in the handbook;
http://emc.sourceforge.net/Handbook/node22.html
it says "Stepper motor control is implemented using a second real-
time task that runs at 100 microseconds. This task writes the
parallel port output with bits set or cleared based on whether the a
pulse should be raised or lowered. This gives an effective period of
200 microseconds for a full up-and-down pulse, or a 5 kilohertz
frequency."

5kHz would be very limiting. Is this still correct? I understand
TurboCNC V4 is testing at around 100 kHz on a fast machine.

Regards,
Mark