Advice for choosing a compatible PC

I want to clarify something here. What you linked to is a motion controller in its own right. Windows is not able to operate in real time so the MAch solution was to delegate motion controll to external hardware running on a small not very powerful embedded controller of some kind.

This contrasts with LinuxCNC where LinuxCNC is the Motion controller. The CPU on the PC has vastly more processing power than the Ma the ch board. We are talking orders of magnitude of more power. But this implies that the dumb eternal hardware used by linuxcnc must be capable of real time performance which typically means it can handle 1000 updates per second. The USB bus is currently not capable of operating with this real time requirement. SO your hardware is useless for Linuxcnc.

This looks a bit sus, seems to be a change in the quoted text regarding the link.

Sneaky spammer got the boot.

I would like to thank you Rodw and thank everyone for their help.
Your comments gave me some informations i was not expecting..

a. BesriWorld wrote above, "If the controller works well, it will not be affected by the latency of the computer."
It is correct finally but i didnt know why.

The following Research cleared to me the way this setup is working, in paragraph 2.
www.researchgate.net/publication/2716157...nd_Motion_Controller .

In paragraph 2 says
"GT400-SV motion control card is embedded in the PC machine through the PCI slot.
Motion control card's CPU and PC's CPU as master-slave dual CPU control mode.
PC front end management for non real time tasks, such as man-machine interface, and other functions.
GT400-SV for real-time tasks, such as interpolation, servo control, I/O etc"

This confirms why Latency for this setup PC+Motion control card is not important.

b. You wrote that a PC with LinuxCNC has vastly more processing power than the Mach board. and its so true.
Why?

My motion controller has 120M working frequency and maximum step-pulse frequency at 1 Mhz
120M = 2.5Mhz. .

PC with J1900 proccesor has 2Ghz perSec.
or
650 MemoryOperationsPerSec on each of its 4 Threads.
2Ghz=800*2.5Mhz,
Even Ferrari vs Tortoise is 340Kmh/*0.5Kmh=680.

No other comment.

P.S.If anyone can suggest me a good motion control card for Linux CNC, i will set the machine in windows for now and will bye the card to change everything as soon as i can.
Sorry for my English and Thank you again.
Evangelos

You already have:
-several PC's with parallel ports
-stepper drives and motors on the machine
So, you can download the wheezy ISO from the downloads page, write it to USB, boot the PC's from it and see what latency you get.
Then, take out the "usb mach3 bla bla" and wire the PC parallel port directly to drive inputs, power on the machine, start LinuxCNC and play a bit, see how it turns out.
You already have everything.
At any time later you can get a Mesa 7i96S or if they become available, any of 5i25 or 6i25 or 7i92.
The first is a full controller with screw terminals n'stuff, the last 3 are the same thing but for PCI, PCI-E or Ethernet and have no screw terminals and are same as 2 parallel port but with much, much faster step rates.

For a stepper based machine look for a mesa 7i96s.
It operates at up to 10 Mhz bu that is faster than required....

What happens with a mesa board is the stepgens are commanded by Linuxcnc to run at a specific frequency which it will do forever unless told to change the Frequency.

Linuxcnc can command the frequency to be changed 1000 times a second. Having the step generation offloaded to dumb external hardware takes a lot of load off the computer and things run better without restriction.