PC latency with Mesa 5i25/ 6i25 card?

Hello,

I'm planning to build a LinuxCNC control with a Mesa 5i25 or 6i25 and a 7i77 connected to servo drives and motors.
Currently I'm figuring out which PC to buy for this project. As far as I understand PC latency is not an issue if you use a FPGA card like the Mesa 5i25 or 6i25. Is that right? In that case I could easily use a refurbished PC with hardware like an Intel core2duo, 4GB Ram... Sorry but somehow I couldn't find a real answer for that.
Thanks and best regards

Julian

Latency is still important when using a Mesa card. It just isn't as critical to have really low latency like you need when software stepping. As it is most modern pc hardware can work if properly configured. A lot of older reclaimed hardware can work well. I have used a number of old P4s and Core2Duos.

Well thanks Todd!
Hm still unsureif I should try and buy a "modern" refurbished office PC (Fujitsu Siemens, Dell, etc.) for around 130 Euro or better buy new PC hardware and self build something for around 200-250 Euro (for example an Intel G4400).
LinuxCNC Wiki says best max jitter under 15000-20000 nanoseconds. But i guess this is without a FPGA card? What sould be the max jitter with a Mesa card for best performance?

If you use a Mesa FPGA card, quite high jitter can be tolerated as long as the jitter is a
small portion of the servo thread period (normally this is 1000000 ns = 1 ms).
I would suggest no more than 100 usec jitter (100000 ns) for a standard configuration

If the DPLL module is instantiated in the FPGA firmware, as much as 500000 ns (.5 ms ) of jitter is fine.

One thing you may want to think about, ie: self build vs refurb office pc, is that the office is more at home in an aircon office environment. This may or may not be an issue depending on your locale. And PSU can be quite $$$$ when they die.
That is something I had to give thought to, the country I live in is usually 3m to 5m away from the sun depending on the time of year.

Just my 2 cents.

Happy New Year to everyone!

@PCW: Thanks for your answer. I decided to build a PC myself. I ordered an Asrock Q1900B-ITX with 4GB Ram and a 120GB SSD.
In that case I will choose the Mesa 6i25, because the Mainboard only have one PCIe.

@ozzyrob: Besides wood dust there is no issue with the environment in my workshop. Never had a problem with normal PC hardware.

Hello! I just found this thread, and I am curious to know was this project successful?
I have also Mesa 6i25 and 7i77 cards and looking for a suitable computer etc...