GMKTec NucBox M5 plus enters the chat

In need of a low-power and small PC which could run conveniently from a small solar power system with a 24V battery bank, I browsed Aliexpress for days and finally settled on the GMKTec NucBox M5. This particular system has two specifically relevant characteristics. First, the SOC has a 15 Watt TDP, and second, it's a Zen 3 and therefore a good match for my big PC.

You can buy this machine with a variety of memory and storage configurations including barebones, with more offered elsewhere than from the manufacturer. I opted for the 32GB/1TB version (you can get as little as 16GB/256GB or as much as 32GB/2TB elsewhere) and it arrived within a couple of weeks. For the around-$300ish price, everything but the GPU is fairly impressive:

SOC: AMD Ryzen 7 5825U (8C16T 2.0Ghz Zen3 with boost to 4.5GHz, and 8 GPU cores)
BIOS: AMI UEFI
RAM: DDR4 3200, 2x 16GB (dual channel)
SSD: NVMe 1TB with MAXIO MAP1202 controller (DRAMless)
Net: Dual RTL8125 2.5GbE and MT7922 802.11ax (WiFi 6)/Bluetooth 5.2 combo

Reviews are mixed, but nobody says GMKTec won't make good on their one year warranty. This machine as configured is reported to pull about 26 watts at full utilization, which is really very little. It supposedly idles at about 10W, which is higher than I'd like but within acceptable limits. This is higher than e.g. an Intel N150-based MiniPC; N95/N100/N150 is the popular Intel chip family right now for people trying to go low power. As little GPU as this machine has, those have far less, and it's really up to the user to determine whether it's worth it to save about five watts. If you're going to use the system as a headless server, then by all means, get an N100 or N150.

I'm running Unigine Heaven in a window at 1080p resolution right now, and the results are very poor, around 20 FPS. They were about the same for X11 and Wayland. If you were hoping to do gaming on this system, you'd better plan to do it at 720p or lower. Modern titles are going to run poorly even at that resolution, I've seen some benchmarks (search for the processor name on YouTube) and games like CyberPunk 2077 are sub-30-FPS.

As poor as the GPU is, the CPU is great. This system really has a lot of processing power for 15W. The 5825U absolutely jumps up and down on the N150, it is about 40% faster at single core and over 4x faster when it comes to multicore (sometimes more like 8x!) and has more than twice the graphics performance. It also has nearly twice the memory bandwidth (Intel supports a bit faster memory, but only with a single channel) to keep all those cores and threads going.

 I plan to use this with a 20" TV/DVD combo I've got which runs off a 12V wall wart. I have a buck converter to let the PC run on 24V coming as well, with the idea being that the inverter in an RV can be turned off at night so as to not pay the standby penalty. (12 volt buck converters are a dime a dozen.) I already have a laptop power supply which will boost 12V to 19V.

This system comes with activated Windows 11 which is allegedly legal; I have doubts about whether it's legal to sell these licenses into this region, but I don't actually care because I have no intention of ever actually running Windows 11. I went ahead and booted it up just to poke at it for a moment before installing Linux, and it was pretty bad. Perhaps it was doing some post-install housekeeping behind the scenes, or the graphics driver just needs an update, but the mouse pointer was actually perceptibly laggy! I installed Devuan testing (Excalibur) which immediately supported everything and worked fine, and there is no lag. I used the GParted LiveCD to resize the Windows partitions down to 100GB or so, and Windows still booted fine. I was able to go into the BIOS (hammer the delete key during boot) and change the EFI boot option to start Debian instead of Windows.

Besides the specs, hardware-wise it's got a reasonably attractive package, and a copper heat pipe cooler. The case is all plastic and feels about average. It comes with a hanger you can use to connect it to a VESA mount. There's 2x USB 3.1 ports and a Type C on the front which will do DisplayPort, there's 2x USB 3.2 ports, 1 HDMI and 1 DisplayPort on the back along with the power connector and some vents for the SOC cooler. The lid can be popped off for access to the RAM and SSDs, which is a nice touch. There's no external WiFi antenna jack, so that can be assumed to have fairly poor range; I am using one of the 2.5 GbE ports. These are supposed to do auto MDI-X, so you can plug machines directly into one another. This would be handy if you had only one port available to you; for example, you could put Linux on it and use it as a firewall and interface for another system, and just wake that machine up when you wanted it to do something.

I tested streaming (only so far with the game Snowrunner) using Steam. My machines are both plugged in to the 4 port 1 GbE switch in my access point. Performance was good, but some detail was lost, so you could tell the difference. I haven't tried with no bandwidth limit yet, but there was no perceptible difference between 50MB/sec and 75MB/sec so I doubt it will be relevant.

All in all I'm generally pleased with this unit so far, and I'm going try to lean on it pretty hard and see how it does to make sure that it fails inside of the warranty period if it's going to. I'm going to set it up to run distcc with my other machine, which is also Zen3 but with 12 cores and 24 threads. I've also just run a linux kernel build benchmark (just defconfig) and got 98 seconds on my desktop and 241 seconds on the MiniPC, but I was expecting something like that since the desktop has mirrored SSDs and twice the RAM.

Finally, it ought to be mentioned that some claim that you can overclock this chip quite a lot, and get almost decent GPU performance out of it. There are no options in this BIOS that would let you do that, so you would have to do BIOS hacking. I also don't see the point of doing it with this particular SOC at this point, because this chip's primary virtue is low power consumption, and for just one or two hundred more you could get a newer system with DDR 5 and more than twice the GPU power. If you're going to put in that much effort overclock something, that would be more worth your time.