Dell Precision Dual-Core 2.6ghz Laptop Gets 3.5 Million NS in Latency?

Yes, it's an old machine, but it would seem that it should be fast enough.

Speed has nothing to do with it. Some old P3s were fast enough. It is built in interrupts that can't be disabled that wreck latency for most laptops.

Yeah, as Todd says laptops are generally not good real time hosts because they have power management hardware/firmware than cannot be disabled and that causes very long latencies. Older machines can have decent latencies, here's a Core Duo E8500
(desktop) running a current Preempt-RT kernel while watching youtube videos, reading email etc etc:

Is that fancy graph part of Linux CNC?

I gave up on the laptop, and now I am trying an Optiplex 755, with 4GB RAM, with a parallel port on the back.
It's a cute little box. I hope it's up to scratch.

Apparently, the Jitter is 43933, and 23482 respectfully, and I am not getting warnings, so I hope that will run my machine.
My machine has a undersized y-axis motor, so I don't need a lot of speed.

The interval numbers are frightening, and I hope they aren't as relevant.

Is that fancy graph part of Linux CNC?

Yes, its the "latency-histogram"

In the example above it was invoked with:

latency-histogram --nobase

because I did not want a base thread

You can get all the options with:

latency-histogram --help

Yes, you can load it from the linuxcnc config picker here.

Thank you Todd Zuercher : )
I would not have looked for it there.