OPNSense on a inexpensive Chinese appliance PC

[ConnerVT]

I didn't want to derail my own thread on building a backup Unraid server to archive media from my main server, so I will start a new thread here.  There is this thread on another forum which currently has over 2700 posts on these appliance PCs, so likely there is some interest in the subject.

 

I originally started by thinking of running pfsense in a VM on my server.  I want to learn some about VM, and figured this to be as good a project as any.  I picked up a dual Intel nic which I put in the server, and continued my research.  Ultimately, I decided that running virtualized on a server that is already tasked with several other important duties wasn't the best model for me.

 

My research kept bringing me to something that's been pretty hot for the past year.  Coming out of China, there have been a number of small fanless PCs with 4 Intel 2.5Gbe ports.  Originally only Celeron based, they are starting to be available with even more powerful processors.

 

I went with a N5105 Jasper Lake based system, which was under $150 USD with no RAM or NVMe included (as I had both on hand).  I seemed to be the best balance of cost, performance, heat and power usage for my home network firewall.  Loaded OPNsense on bare metal, though there are many folks running Proxmox with a number of packages on these little boxes.

 

You can read the thread I linked above, if you have several hours to kill.  If not, my tl;dr is -

 

A solid little system.  It has a few weak points.  One is the supplied power adapter is a bit questionable.  Most people who would be doing this likely have a better quality one (12VDC) they can use.

 

The other is the CPU heat sink assembly from the manufacturer is pretty shoddy.  Mine shot up over 90 C throttling just running CPU-Z benchmark (not the stress test).  The CPU die is bare (no integrated heat spreader) which contacts an aluminum block screwed to the top case/heatsink.  With a lot of (I'll assume) cheap thermal paste.  I disassembled this and using sandpaper, smoothed the block and case, removing burrs and anodization.  I added a thin copper shim and some quality paste.  Stress tests over time now sit in the 60-70 C window, well within the Celeron's acceptable range.

[JonathanM]

5 hours ago, ConnerVT said:

I added a thin copper shim and some quality paste. 

Be very careful with the amount of stress you put on the circuit board. Ideally you should be pushing directly opposite the CPU with a spring force of some flavor, so the circuit board is floating with respect to the hold down screws. The pictures you posted appear to show the only force applied to the CPU - heatsink interface is from the tension created screwing down the board.

 

Perhaps a pair of 3D printed blocks with a spring inside? That way the CPU - heatsink are clamped by the case screws.

 

Ignore me if I've misinterpreted the pictures and description.

[ConnerVT]

You have a valid concern, Jonathan.  I've worked in semiconductor manufacturing for nearly 25 years.  Once a die has its passivation layer it is much less fragile.  You still need to use care, take your time to align things correctly and avoid twisting or flexing.

 

In this case, the N5105 has CPU and GPU dies mounted on an interposer, which has a stress collar around the outer edge.  The copper shim I used (0.8mm) added little stress, as it took up the space poor fitment and the sanding done to remove burrs that existed around the screw holes drilled in the aluminum block and top case.

 

Unless a person thinks every task requires power tools and a hammer, it is not all that challenging for someone with at least moderate skills.