sudden unexplainable axis lag

Hi, I just need a bit of guidance - I have up until today been running LinuxCNC perfectly on an Intel Atom-based computer via the parallel port

Today I noticed that when I am manually moving axes around via the keyboard sometimes after I release the key the axis keeps moving. This happens on the Y and Z axes but never on the X axis. I've never seen this before. You can imagine when the Z axis doesn't stop it's a little disconcerting

Assuming that my computer had developed bit rot I replaced the SSD, reformatted the machine and installed the latest LinuxCNC.

I then installed a generic stepconf and copied my old .ini files over the top of the new ones.

However, the behavior didn't change and even in ghost running a couple of jobs I can see where the Y axis is lagging the X axis.

What is the most likely place for me to look for the problem? I realize that "your ini files" is the obvious answer, but I'm trying to figure out why this happened today on a machine that was working perfectly 2 days ago. I had not done any software updates in that time.

Alternately is it time for me to grow up and just get a Mesa card and a modern motherboard?

Thank you,

DougM

The first symptom sounds like the user interface is slow or losing characters,
not sure why this would start happening on a system that had been OK but I guess
it could be hardware (thermal throttling? failing mouse/ keyboard?)

I would not think this would affect actual machining if you are not getting real time errors or
following errors

Have you tried to control ald GND wiring?
Have you controlled the earth between pc an machine?
Can you measure pulses on the according driver inputs?

What version of linuxcnc?