I am working on a project to make a barn-door camera tracking platform
using a stepper motor connected to the printer port on a PC. If the
project meets expectations, I hope to publish an article in an
astronomy magazine. As an exercise, I want to be as anal as possible
in sending the stepping pulses to the motor.

The main loop of the program will be:

- Load a pre-computed value into an interval timer
- Send the proper output bits to the printer hardware port
- Compute the next value to be loaded in the interval timer
- Suspend the process

After calculating the next interval timer value (based on the geometry
of the barn door), it is necessary to reduce the value by the amount
of time it takes to wake up the process and load the next interval
timer value. Obviously this means that the application will have to
be calibrated for the system on which it is running.

Two questions:
1. I hope to make this application available as an executable that
would run under a live distro of Ubuntu. To minimize the impact of
other processes on the accuracy of the application, I would like to
generate a script to kill all un-necessary processes (communications,
plug and play, etc.) Can anyone recommend a list of processes that
might be deleted? I suppose that processes that activate on a
hardware interrupt (other than the RTC) are harmless. (I am willing
to assume that the system may need to be rebooted when the user wants
to end the application.)

2. Does the system know the absolute value of one jiffie for the
hardware it is running on, or is it necessary to calculate it?