Old PC`s and Mach3

[magicniner]

I have a ibm t42 laptop running xp and i use a paralell port to the driver board. I use a cpu program called rightmark CPU clock utility, without it i get judder on the steppers with it i get smooth running, its a free utility google it

That utility effectively over rides the laptop power management's propensity to slow down the CPU whenever possible to reduce power consumption, another common laptop problem is a parallel port voltage which proves marginal for driving external logic.
You have a laptop which can work with Mach3 through the parallel port, many will not and that's the reason laptops were not recommended or supported.