Latency of parallel port system on decent hardware.

I have LinuxCNC 2.9.3 running on Debian Bookworm installed on a decent old PC.

The latency test returned a max jitter of about 15ns for the top number and 24ns for the bottom number.

I have now removed all unnecessary hardware and peripherals.

I will also blacklist as many kernel modules as possible.

The CPU scaling governor is set to performance.

The PC communicates with the microstep drivers directly through a PCI-e parallel port card, a parallel port cable, and a PMDX-122 buffer board.

Is this latency acceptable?

Would LinuxCNC 2.714 Wheezy work better for my setup?

I will post latency test result after disabling all unnecessary hardware.

Is it worthwhile to disable the Ethernet port (blacklist e1000e) to reduce latency?

For the lowest latency, you might have better luck with RTAI than PREEMPT_RT, assuming the BIOS isn't buggy:

forum.linuxcnc.org/9-installing-linuxcnc...ng-rtai-debs-for-2-9

If you need help, let us know!

I managed to lower the latency to about 14000ns max jitter by disabling hardware.

I also set the CPU governor to performance.

I will try to disable more hardware to further reduce latency.

Unfortunately, I am unable to modify and BIOS settings because this is an old scrap computer from my high school.
I tried to get the IT person to change the password, but the BIOS login window is broken

I also unplugged the front audio and USB ports that I do not use.

(The back of the PC has a plethora of ports)

However, now the BIOS complains every boot

Whatever, I'll just press f1 every time I boot up to clear the error.

Running "sudo apt update && sudo apt install linuxcnc" gives an error.

I blacklisted the Ethernet port.

Debian has no internet connection.

BTW, the system is a dual boot of Ubuntu 24.04 (my preferred OS) and Debian (for LinuxCNC)