I had fun playing with the GMKtec NucBox3, an interesting and capable little PC more affordable than Intel's NUC product line, naturally with some expected tradeoffs for its lower cost. I learned about these little PCs from a Newegg advertisement and, between the time I ordered one and its arrival, I had a failed USB external drive that I transplanted into a small form factor Dell PC. Computers in these two projects represent a spectrum that I should keep in mind for future project possibilities. Which one I buy would depend on a project's requirements.

Intel NUC

A genuine Intel NUC would be more expensive than any of the other options below, but sometimes it's worth spending that money. For example, if I'm building a solution that needs to be reliable, I will pay more for a brand name. Or if I want to design something that can be repeated by others, it's easier for someone to buy an identical Intel NUC than to find, say, a GMKtec. For this reason: If my Sawppy rover ever changes over to an x86-64 PC ROS brain, the official recommended hardware will be an Intel NUC. (Supplemented with suggestions on what to look for in lower-cost alternatives like the NucBox3.)

Just Below $90

But when we're feeling adventurous and not particularly motivated to pay for quality or consistency, we can go bargain hunting. Searching for various options, I observed a price floor somewhere in the $80-$90 range. I see an interesting hint of economic factors at play preventing things from much lower than $90, but I don't know what they might be. (As a point of comparison, Raspberry Pi 4 8GB MSRP is $75.)

Lowest Bidder du Jour

Amazon categorized these products under: "Electronics" > "Computers & Accessories" > "Computers & Tablets" > "Desktops" > "Minis". Sorting them by price today, I see several options right around $89, roughly 40% discount from the price of a NucBox3. To get to that price point we have to give up many things. For example, this item (*) made some notable tradeoffs:

  • Memory is half the size (4GB vs. 8GB), uses older technology (DDR3 vs. DDR4), and is soldered in never to be upgraded.

  • Storage is half the size (64GB vs 128GB), uses much slower technology (eMMC vs. SATA) and is also permanently soldered. However, it does have a 2.5" SATA bay, which the NucBox3 does not.

  • CPU is three years older and from a different product generation (Celeron J3455 vs. J4125) and it doesn't meet hardware requirements for Windows 11.

On the upside, it still meets all my hard requirements for robot brain: 64-bit CPU running x86-64/amd64 instruction set, gigabit Ethernet port, small, lightweight, and might run on battery power. Depending on future project requirements, I may choose these tradeoffs in favor of a <$90 bargain.

Buying Refurbished

Looking at inexpensive PCs on Amazon, I saw a lot of refurbished units. Clicking around a few listings, I learned Amazon had set up an entire department. "Amazon Renewed" is dedicated to refurbished products of all kinds, not just computers. I should definitely keep this in mind as an option. Given my personal experience, I'd restrict my search to refurbished Dell products from their corporate line. Which would still leave me with very many options. Check out these guys, each offered at a few bucks under $90:

  • Optiplex 3040 Micro Desktop (*) are bigger than an Intel NUC, but tiny compared to anything else. Skimming Dell's manual, I see a 2.5" SATA bay inside. I also see what looks like a M.2 slot on a picture of its mainboard, but M.2 isn't called out in the manual as a storage option. I see a gigabit Ethernet port and it accepts power from a DC barrel jack, so there's a possibility it can be persuaded to run on battery power.

  • Optiplex 790 USFF Desktop (*) are significantly larger. Packing an optical drive on top of a 2.5" drive bay and AC power supply. No robot battery power for this machine, but dual 2.5" drives are possible via an optical drive caddy. This could work for TrueNAS replication target if my storage drive is a high capacity 2.5" laptop hard drive.

  • Optiplex 3020 SFF Slim Desktop (*) is a successor to the Optiplex 960 I repurposed to a TrueNAS replication target, with at least one 3.5" drive bay and one optical drive bay. This would be my default choice if I need to build another replication target machine.

What if I want a parallel port for LinuxCNC? Sadly, that's an uncommon enough request I can't filter on Amazon. But when it comes to refurbished small Dell PCs, Amazon Renewed is not the only game in town. There are plenty of other vendors like PC Liquidations, who offers filtering by parallel port. Resulting in a list of refurbished Dell Optiplex with parallel port starting at, you guessed it, a few dollars under $90. All good options if I want to dedicate a cheap PC to a task, which usually also requires me to set up automatic software updates.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.