Introduction

When my laptop met its untimely demise, I was on the hunt for a new computer to run LinuxCNC for my CNC projects. In this post, I’ll discuss my experience with the Dell Optiplex 7050 Mini, featuring an Intel Core i5-6500 processor, and determine whether it’s the right choice for LinuxCNC enthusiasts like myself.

Dell Optiplex 7050 Mini – Key Specs

The Dell Optiplex 7050 Mini is a compact, yet powerful computer that comes with the following specs:

• Intel Core i5-6500 Processor (6M Cache, up to 3.60 GHz)
  
• Up to 64GB DDR4 RAM – Mine is fitted with 8GB
  
• Integrated Intel HD Graphics 530

• Penty of USB ports , and a 256GB SSD fitted

• Plenty of these units are available used through third parties. I bought mine for 150$

These specs seemed promising for running LinuxCNC, but the true test would come in the form of latency testing and real-world performance.

Installing Debian 12 + LinuxCNC + Probe basic in 2023

I had previously made a post about installing LinuxCNC 2.8.4 with Probe Basic, but unfortunately, there are several broken repositories in the probe basic installation script… so I was forced to install LinuxCNC 2.9 on Debian 12 using the instructions posted on the developer’s website and that worked … mostly. So I devoted a new post relating to how I installed it and the small challenges I faced.

Read more about it here: [placeholder]

Latency Testing for Dell Optiplex 7050 Mini LinuxCNC

Latency is a critical factor for LinuxCNC, as it determines the system’s ability to respond to changes in the CNC machine’s position. Lower latency results in smoother and more accurate operation. To evaluate the Dell Optiplex 7050 Mini, I used the LinuxCNC ‘latency-test’ utility to measure the maximum base thread and servo thread latencies.

As I’m using a Mesa 7i96S the base thread is not actually not applicable but I still had it running in my tests.

LinuxCNC BIOS Modifications for Dell Optiplex 7050 Mini

I did some small modifications in the BIOS setting to hopefully make LinuxCNC run smoother on the Dell Optiplex 7050 Mini. I basically disabled any power-saving features, sleeping states, and any virtualization options. I left the “turbo” feature of the CPU on, as I was unsure if this would benefit or harm the latency results.

Grub Modifications for Dell Optiplex 7050 Mini LinuxCNC

I did some modifications in the Grub including isolating CPU cores for LinuxCNC and reducing sleep modes and states for the Intel i5-6500 CPU on the Dell Optiplex 7050 Mini.

Follow the instructions provided in the original article to perform these modifications.

at the terminal, type:

sudo nano /etc/default/grub

when this opens, add this line (for a 4 core system):
GRUB_CMDLINE_LINUX_DEFAULT="isolcpus=2,3,4 intel_idle.max_cstate=0 processor.max_cstate=0 idle=poll"

You can add this below the other command line parameters in the file. Then hit control-x to save it.

then type:

sudo /sbin/update-grub

then reboot.

Verify that it worked by doing:
sudo dmesg
or
cat /proc/cmdline
which shows the parameters used for the current bootup

You should see your isolcpus command in that list.

This modification was inspired by this PrintNC wiki article.

Note: I have not independently verified if the idle max, state and idle poll settings benefit.

Comparing the Modifications

I read somewhere that there might be a performance benefit by isolating a CPU core pair i.e. 2,3 for a 4 core system instead of separating random cores so I did a quick test:

This test was conducted with 4x glxgears running and YouTube full HD video in the background.

The isolcpus 1,2,3 option resulted in lower latency, hence that is what I kept.

Results of Dell Optiplex 7050 Mini LinuxCNC Latency Test

The Dell Optiplex 7050 Mini performed admirably in the latency tests. The measured latencies were well below the recommended maximums for LinuxCNC, which means that LinuxCNC should be running smoothly on the Dell Optiplex 7050 Mini. However, it’s worth noting that individual results may vary depending on the specific configuration of the computer, as well as the connected CNC hardware. I’m utilizing a Mesa board for the direct control of my servo motors, so the latency requirements are also much less strict.

Conclusion: Dell Optiplex 7050 Mini LinuxCNC – A Solid Choice

Based on my experience and the latency test results, the Dell Optiplex 7050 Mini with the Intel Core i5-6500 processor is a solid choice for running LinuxCNC. Its compact form factor, powerful processor, and compatibility with Linux make it a reliable option for CNC enthusiasts. At ~$120 for a fully tested and working unit with 8GB RAM and a 256GB SSD, the Dell Optiplex 7050 Mini LinuxCNC is also cost-effective.

However, keep in mind that the ideal computer for LinuxCNC depends on your specific needs and budget. It’s essential to evaluate your requirements and research other options before making a final decision. Overall, the Dell Optiplex 7050 Mini LinuxCNC stands out as a cost-effective and capable choice for those looking to run LinuxCNC on a reliable system.