LinuxCNC not connecting to 7i96S on 2.9.1

tomorrow ill try reinstalling linux with version 2.8.2, and testing it out on a raspberry pi 4. I understand my latency is worse than what you showed but only by 3-4x. I hope that linuxcnc would have some tolerance without freaking out over a small difference? at least to connect and start the program.

I'm not sure what the exact problem is, but a PC that has no
access to power management setup is not likely to be a good
candidate for running LinuxCNC (It would be similar to a laptop
which are also not suggested for hosting LinuxCNC)

The "resource unavailable" error might also indicate loss of link
So checking the yellow link LED on the 7I96S's RJ45 connector
when you get the error might be worth a shot
 

Are mini PCs suitable to run Linux cnc? Anything I should look for specifically? I like to keep my computers running most of the day so having it small helps a lot. Would the following work?
HP EliteDesk 800 G2 Desktop Mini Business PC, Intel Quad-Core i5-6500T up to 3.1G,16G DDR4,240G SSD,VGA,DP,Win 10 Pro 64 bit
a.co/d/h4FURtk

I have an EliteDesk 800 G2 that works very well but its the 65W version
with the 3.2GHz I5-6500 rather than the 35W 2.5 GHz I5-6500T version you
listed.

There is a post on this forum that says the  35W 2.5 GHz I5-6500T version of the G2
will work in UEFI  mode but If I had a choice, I would use the 65W  3.2 GHz I5-6500 model.

It might be a bit different if you install linux over your chromebox but I play with Linuxcnc sims on on my chromebook using the linux terminal.
Recently that has advanced from Bullseye to Bookworm and I have been unable to open axis despite pncconf and latency-histogram being able to run. I suspect its something to do with Wayland but previous fixes dont solve it. The long and the short is that I would never consider chromebook/chromebox being suitable for Linuxcnc.

Hint. Interface is provided by Quanta Computer Inc., apparently. Anything you guys can find related hardware specific on the linux venues?

mac.lc/address/54:AB:3A

@rowow - I also had this low latency issue on a Marvel Tech interface. Like yourself I was getting similar 0.300ms ish avg and miraculously enhanced it down to a fast & steady 0.04ms using below.  

Using ethtool --coalesce
$ sudo apt install ethtool
$ sudo ethtool -c eth0
( take notes of your rx-usecs and tx-usecs defaults. Mine were 100 and 1000 respectively)
( start Linuxcnc and have it connected to the card)
( Time to dial/tune)

$ sudo ethtool -C eth0 rx-usecs 50
$ sudo ethtool -C eth0 tx-usecs 500
$ ping ip.ip.ip.ip
....
$ sudo ethtool -C eth0 rx-usecs 25
$ sudo ethtool -C eth0 tx-usecs 250
$ ping ip.ip.ip.ip
....
( Repeat tuning until you get satisfactory latency and no lcnc task/axis pos errors, etc. )
( Once everyone's happy, save those in your interface conf. )

$ sudo nano /etc/network/interfaces

***********************************************
      # The loopback network interface
      auto lo
      iface lo inet loopback

      auto eth0
      iface eth0 inet static
      (... ... static address stuff)
      hardware-irq-coalesce-rx−usecs 25
      hardware-irq-coalesce-tx−usecs 250
***********************************************

$ sudo systemctl restart networking

my issue is linux CNC doesnt connect to the card in the first place. See the OP for the error code regarding
"hm2_eth: rtapi_app_main: Resource temporarily unavailable (-11)"

Yeah, saw that. I was getting the same over a dead slow ethernet link. My ping was well over 0.300~0.400ms OOTB install. Sorted though, with the ethtool hack above. "Marvel Technology" chipset.

Try that and see if you can at least connect to the card with this:

###HAL
#setp hm2_7i96s.0.watchdog.timeout_ns 5000000
setp hm2_7i96s.0.watchdog.timeout_ns 50000000

###INI
[EMCMOT]
#SERVO_PERIOD = 1000000
SERVO_PERIOD = 5000000