Mini PC for LinuxCNC/CPU Realtime Performance

I’d like to replace my weak HP EliteDesk G2 on which I currently run LinuxCNC. In my setup, the PC drives a Mesa 7i95t over ethernet, and displays a LinuxCNC UI on a monitor. Form factor is important since the PC is only used for LinuxCNC.I’m looking at various options for ~$800 range mini PCs, but am struggling to understand how they will perform in a realtime environment. Some of the options are:

• Beelink EQR7, cpu: AMD Ryzen5 7535U
• Beelink SER9 PRO+, cpu: AMD Ryzen7 H 255
• GEEKOM GT13 Pro, cpu: Intel Core i9-13900HK
• ASUS NUC 14 Pro, cpu: Intel Ultra 7 155H
• MINISFORUM DeskMini UM870, cpu: AMD Ryzen 7 8745H

Could someone please help shed some light on how to evaluate whether these models will perform well running the LinuxCNC realtime environment?

Thanks!

I think best bet is to keep the G2 and try to optimize it for LinuxCNC.

1.) Disable all power saving options in the BIOS
2.) Update your grub CMD line to include: max_cstate=1 idle=poll isolcpus=(your last CPU core)
3.) Set up IRQ affinity (see below)
4.) Disable IRQ coalescing (see below)

forum.linuxcnc.org/38-general-linuxcnc-questions/47974-grub

forum.linuxcnc.org/38-general-linuxcnc-q...irq-affinity?start=0

forum.linuxcnc.org/38-general-linuxcnc-q...g-for-intel-ethernet

A newer or more modern PC can be sometimes worse and it's a bit of a gamble if it works out of the box.

Once you address 1 - 4 you are in control on how well your PC works with LinuxCNC.

Thanks for the reply! I’ve done all that so I believe my G2 is optimized for LinuxCNC.

However I’m a bit limited by the low ram (8GB), low disk space and etc.

I realize newer models are risky, therefore some of the models I am looking at are far from new generation CPUs (like the Ryzen5 7535U).. Or is CPU not the only potential issue, but also things like the motherboard etc?

Many of us run systems with much lower spec CPUs, like Celeron J1900, i3-6100, N100, N150 with good result. 8GB should be plenty.

What does your latency-plot look like?

giaviv wrote:

However I’m a bit limited by the low ram (8GB), low disk space and etc.

8GB should be fine, and how low is "low disk space"? Linux starts complaining only when you get under 1GB of free space, so anything above is fine.

giaviv wrote:

I realize newer models are risky, therefore some of the models I am looking at are far from new generation CPUs (like the Ryzen5 7535U)..

7535U is not "far from new", it is new and still in production, Zen3 with 15W TDP, so it is a laptop CPU and this may be bad for latency, although not always.

giaviv wrote:

Or is CPU not the only potential issue, but also things like the motherboard etc?

CPU's are mostly fine as they can change states and do stuff, mainboards are usually the latency killers depending on quality, BIOS implementation, power saving options, etc, etc, way to many to list here, but mostly bad/weak CPU power stage set to work at the edge and throttling the CPU to save itself from going up in smoke.
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As a general rule, i would stay away from those small PC's, they are cute and stuff, but way to limited thermally, the xxxxU versions are fine, but a 13900 ... oh hell no, it will be limited thermally to something like a good 4 core CPU when under load, and they fail but being limited will prolong their life a lot so...
There were some NUC's that were OK for LinuxCNC way back.
After all this, there is no way to know for sure if any of those will be OK, short of buying and testing.

giaviv wrote:

Thanks for the reply! I’ve done all that so I believe my G2 is optimized for LinuxCNC.

However I’m a bit limited by the low ram (8GB), low disk space and etc.
 

This is nonsense! 4 gb RAM is fine for LinuxCNC but it will tolerate 8gb without ill affect. Linux is more memory efficient than Windows.....