Installing Linuxcnc and Debian Bookworm on problematic hardware (eg. Realtek NIC

I'd look in synaptic. its only 1 version behind where bookworm is (now 6.0) so its probably there. 
Install bookworm non-free (you may not need to do), roll the kernel back in synaptic, install matching headers, sudo apt install linux-headers-($uname -r)
then don't worry about preempt-rt which linuxcnc will install.

Worth a try. I do know one guy who solved issues on an H2 with the realtek driver.

I punted before you responded.

Bullseye is up, and Joco's script has RT 5.10, LCNC, and Probe Basic up and running without any obvious issues so far.

Running the latency script now - so far, so good.

As you said - don't touch it!

I just updated the second post to fix something a user found confusing and added some notes about how to solve a recent  issue with Bookworm and Bullseye per this issue
github.com/LinuxCNC/linuxcnc/issues/2264
Note this does not let Gmocappy run and I have reported that to Hans.
 

Rod,
Thanks, your instructions have helped me a lot,  Also your Youtube video on installing from source.  Thought I would add some further thoughts on this topic that might be of general interest.

I'm in the process of building a second CNC machine using LinucxCNC. This is also a Taig, but this time a lathe.  The current PC I use for the mill is getting long in the tooth so I thought it was a good chance to try one of those small cheap mini PCs, given the current cost of R-Pis.  The PC is a Kamrui AK1 using an N5105 processor from Amazon.  It's got better specs than the well-known GK1 mini, but the N5105 CPU puts it in the category of "problematic hardware"

I was impressed with the way it handles Windows 11, seems quite responsive for such a low end CPU.  I wanted to check the latency before going much further, so I booted the LinuxCNC 2.8.4 live USB.  However, it stalled with some repeating messages about SDHCI hardware, whatever that is.  Next I tried the bullseye live CD.  This booted and installed (to an add-on 500GB 2.5" HDD) just fine, but no WiFi and only 800x600 graphics. The Intel graphics HW in the mini PC seem to need a bookworm 6.x kernel, which I got and installed as Rod described, no problem.  The WiFi HW is the Realtek RTL8821CE, and no Debian package supports it,  so I built it from github source (github.com/lwfinger/rtw88).  Again, straightforward once you find it.  The ethernet HW/FW worked out of the box, but I haven't tried it with a Mesa card yet.

For the LinuxCNC, apt did not work.  synaptic listed the 2.9 packages but would not install them (held broken packages). I tried to set up repositories and keys, but it was very confusing:  which repositories, which distro? How do you get the key, now apt-key does not work?  Perhaps someone can describe a way to set up the repositories.

So I ended up building LinuxCNC from source, as described in Rod's video.  I like the CNC menu rather than CLI, so I built a deb and installed that - all straightforward so far.  Earlier I'd built "run-in-place" which also worked fine.

As a matter of interest, the latency jitter looks pretty good, being of the order of 50000 - 60000.  My older PC using an FX8570 CPU works very well and comes in just under 100000, so the mini should work at least as well.  By the way, if you inadvertently choose the wrong kernel in grub and test the latency, you will be horrified:  8,000,000 nS jitter.  Stupid mistake, but now I know what the realtime kernel does.

So it looks like these mini PCs are viable, but need a bit of setting up.

Great stuff. Running the 2.8 installer from Linuxcnc, you end up with Debian Buster which does not have Linuxcnc in its repos.
I'm glad it built linuxcnc for you. 
You could probably improve latency by adding isolcpus=2,3 to the boot string in grub. (it will likely say quiet now so add it after that) I use grub-customizer which makes it easy but it may not be in Buster.

The CPU is not the problematic bit. Its if it has a Realtek or Broadcomm NIC

Another try is to install the firmware-realtek package. In my case, the dkms drivers improve the network latency too. Just the firmware package got little better result in my case. If installed, should ethtool print like this.

sudo ethtool -i enp1s0 
driver: r8169
version: 6.1.0-3-rt-amd64
firmware-version: rtl8168h-2_0.0.2 02/26/15
expansion-rom-version: 
bus-info: 0000:01:00.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: yes
supports-priv-flags: no

 sudo dmesg |grep firmware
[    5.138392] r8169 0000:01:00.0: firmware: direct-loading firmware rtl_nic/rtl8168h-2.fw

Yesterday i order new Intel network card. I will report what happens. For long time i though Linux and realtek are good friends, just now i will check this out who is tux best friend.

The Network Card arrived today and i did a quick driver check.
Result; PCI Express Realtek card with firmware driver is little better than PCI Express intel card with 82576 NIC. 
Also, tmax times to mesa card is with realtek card little better. 
So i believe it is a general Debian problem.

Did you set the coalescing setting as per the linuxcnc hm2eth component documentation?
The ping times look pretty good. Run them  up for a while and report back and include tmax settings

To test ping latency:

sudo chrt 99 ping -i .001 -q 10.10.10.10

and run for a day or so while torturing the computer with
you-tube videos etc

Today i made a different test. 
1. Network card configuration over the network-manager-gnome tool
Ethernet controller: Realtek 
Driver r8169
firmware-version: rtl8168h-2_0.0.2 02/26/15

740436  hm2_7i76e.0.read.tmax
1170167  servo-thread.tmax
Quick ping check AVG time: 0.062

Ethernet controller: Intel Corporation 82576 
driver: igb
firmware-version: 1.2.1

1287877  hm2_7i76e.0.read.tmax
1745947  servo-thread.tmax
Quick ping check AVG time: 0.078

2. Network card configuration direct /etc/network/interfaces and the network-manager-gnome tool delete complete

file snip
#Ethernet controller: Intel Corporation 82576
auto enp2s0f0
iface enp2s0f0 inet static
address 10.10.10.1
netmask 255.255.255.0
hardware-irq-coalesce-rx-usecs 0

#Ethernet controller: Realtek 
auto enp1s0
iface enp1s0 inet static
address 10.10.10.2
netmask 255.255.255.0

Ethernet controller: Realtek 
2622746  hm2_7i76e.0.read.tmax
2721611  servo-thread.tmax
Quick ping check AVG time: 0.082

Ethernet controller: Intel Corporation 82576 
820478  hm2_7i76e.0.read.tmax
1120263  servo-thread.tmax
Quick ping check AVG time: 0.072

I not search for any spikes in *tmax times. Maschine was running for 5 min and no stress on pc. But the difference is unbelievable.
It seems i makes a huge different how to config the card. But in the time on both near equal. Just intel has to config over /etc/network/interfaces and realtek cards need the non free firmware driver and config over the network-manager-gnome.