Category: Installing LinuxCNC
I would like some advice please on how to proceed with the computer I am using to run LinuxCNC. I have just installed the latest version of LinuxCNC (2.9.3 Debian12 Bookworm Preempt -RT) and have run the Stress Test for an hour - the figures are not encouraging: 85953ns max jitter. I know this is way too high, and if I were to use this computer I would have to make some changes, or it might be that no matter what I do it will not be suitable for software stepping. If so I might have to save-up for a Mesa Board and do the stepping there. The problem is that I have no real feel for what scale of improvement various changes might have.
The computer is a Dell Optiplex 745 with an Intel(R) core (TM)2 CPU 4300@1.8GHz. It has 6GB of DDR2 SDRAM and is using the on-board graphics card. I know the graphics card is the first place I should look to make an improvement, and I have the opportunity to buy an AMD Radeon 450 with 4GB GDDR5 - but it is not that cheap. I have a simple 3 axis cnc mill with just 3 Nema 23 stepper motors, but I would like to upgrade it at some future point.
My first question is: in very general figures, is it realistic to think that a new graphics card might reduce the jitter figure by, say 60000ns, or is this too optimistic - is it even worth a try? If any new graphics card could not make this scale of improvement it might be better not to buy the Radeon and put the money towards a Mesa board.
My second question is: if I were to buy the Mesa board would I still need to upgrade the graphics card anyway, or could I stick with the on-board card?
Finally,(preparing my self for the worst !), I have been looking at the range of Mesa boards available and it is a little confusing for a novice. The advice on this site seems to be a year or 2 old, and so I would be most grateful if you could recommend the most suitable board for me. I cannot imagine I will ever require more than 5 axis - I probably will stick with 3, but I might double up the motors on Y. I need the ability to control the spindle (1500Kw 24000rpm currently using a Chinese VFD), and the mist (just a compressed air feed).
Grateful for any pointers
Mitch
