Choosing OS/kernel and upgrade issues

So i have a Dell Optiplex 780 SFF with 8GB and an E7500 using on the integrated GPU. Getting it setup for software stepping via integrated parallel port. Going to be signaling a C10 BoB and some Automation Technolgies Steppers/drivers for a G0704 Mill. Trying to pick out the best path forward software wise. For now trying a little of everything. right now I am triple booting OS's.


-W7 (mach 3 etc)
-LinuxCNC 2.8.0 Debian 10 Buster PREEMPT-RT ISO (upgraded to 2.8.1)
-LinuxCNC 2.8.0 Debian 7 Wheezy RTAI (2.7.14)

I don't have any extra needs of the PC other than driving the machine. I don't really care which OS is there, just whichever gets me the best performance (lowest jitter etc?). I installed the wheezy because it said its the most stable RTAI and probably the lowest latency but I'm not opposed to doing the Buster RTAI if there is value in it. from what i can ascertain there only is if you have extra needs for hardware compatibility. I'm running the latency script as i type this in PREEMPT-RT buster for 2hrs so we'll see what we get. Shorter tests earlier had me in the 20-35 range with the 'base' in the script set at 50. Seems like the consensus is that would be just fine but maybe the RTAI might be a little better. I did all the disabling of extra cores and bios features etc. could also pickup a cheap GPU if its useful.

So the questions...

1) Buster PREEMPT-RT, Buster RTAI, or Wheezy RTAI?
2) The Wheezy iso installs LinuxCNC 2.7.14 that you have to upgrade. Of the 3 items needing to be upgraded in the repository (deb linuxcnc.org wheezy base 2.8-rt) one seems to be failing. "linuxcnc-dev' errors out saying its either too old or missing from repository. I cant find a way around that. I don't have the exact message and the PC is tied up in the script right now but i think that was close enough. any tips?


Thanks All!

Thanks!

1) Figured that would be the answer. Didn't know if there was a commonly known precedence already noted between Buster RTAI or Wheezy RTAI for latency. If there are no other software advantages ill probably just stick with Wheezy since apparently its error free and i dont have to do another OS install. Can you swap back an forth between Buster RTAI and PREEMPT-RT without issue? I see there is a way to go one way

This was my Buster PREEMPT-RT latency data :
rtpreempt.lat: 7201 secs base min: -27.800 uS max: 31.600 uS sdev: 1.600 uS
rtpreempt.lat: 7201 secs servo min: -39.400 uS max: 38.400 uS sdev: 1.800 uS

What kind of numbers am i shooting for? under 50 or under 25?

2)indeed. I'll have to run through it again but iirc in step 1.2.1

"Click the check box to mark the new linuxcnc and linuxcnc-doc-* packages for upgrade. The package manager may select a number of additional packages to be installed, to satisfy dependencies that the new linuxcnc package has. "

one of the additional packages is the 'linuxcnc-dev' one. Thats the one that is giving the error message that its not present or too old. I'll get the exact language later. seems like something is up with the package in the repository...

Edit: screenshots added

I only included the dev because when you include the base one it automatically adds it. For that reason i figured it needed it. What do you mean by 'build components"?

Anyways i let it remove that and only install linuxcnc and linuxcnc-doc-en and it went through. Oddly despite being on the 2.8 repositories it started on 1.2.7.15 and said it was going to upgrade to 1.2.8.1. When it was completed it listed 1.2.9.0 as being installed. I'm not certain what happened. Is 1.2.9.0 stable?


EDIT: I found out how to force 1.2.8.1 and successfully did that. The 1.2.8.1 linuxcnc-dev is still broken though and cannot be installed. Is that something that needs to be fixed on the other end or is there another place i can download and manually install it?

Its for a direct integrated parallel control 3 Axis G0704 Mill with these steppers and drivers . I just wanted to get in the ballpark of where i need to be on the software side while i wait for some other supplies to come in.

It seems like the RTAI should have the lowest latency for my applications. I have the Wheezy setup now with RTAI and 2.8.1 although missing the dev module due to the error. I've got no problem converting the Buster over to RTAI if there is some advantage i dont know about. from what i can tell there are still some bugs with that combo and it doesnt seem to have extra benefit for my uses... unless i missed something.