Tracking down stuttering (deb-12, LinuxCNC-2.9)

Plotting the following error will show if G0 motion perturbations are from the
drives/powersupply//timing or LinuxCNC/RT related issues.

I think you are back learning how to use halscope and follow PCW's advice.
Is the keyboard a wireless one by chance? if so replace it with wired.

Many people have had excellent results with Bookworm.
Many people are using Linuxcnc 2.9 without issues (myself included)
Many people are using the 7i96s without issue including with 2.9 and Bookworm.
Everything points to an external issue but you need to fire up halscope to eliminate the software/mesa side of tihngs

If you are not using the spindle encoder, or PCW can give you the ENC inputs of the 7i76e with a bitfile, look at wiring a MPG direct to the Mesa card to avoid the keyboard,

I'm waiting for the PREEMPT_RT patch to be pushed to the mainline code. I think that missed the 6.4 kernel but might be on the 6.5 kernel. That will be a kernel worth building!

Thanks, I'll try halscope next time I have a chance to debug the machine.

I'm seeing the same issue with wireless or wired keyboards and do have a spindle encoder (the spindle on this machine is a 3.5hp servo).

Ah, maybe  add a 7i73 for MPG support once you get past this current hurdle. keyboard jogging is not something I've ever really done until recently.

I didn't see any following error and don't think I'm loosing steps. It might just be the cheap stepper drives (this machine uses generic TB6600 drives as standard -- they are about $10ea on Amazon). I ordered a nicer Leadshine EM542S drive for X to see if it makes things smoother, if so I'll upgrade to those on Y1 and Y2 as well.

New drivers made all of the difference. Life is too short to try and debug cheapo ones.