Matching compatible mini-PCs with RAM / NVMe on hand
January 19, 2023 7:09 AM   Subscribe

I've recently upgraded a few laptops and have some NVMe drives and spare RAM on hand. Rather than letting them gather dust or try to sell them online, I'd like to match them with inexpensive mini PCs for use in my home lab. Best way to backwards-match this?

I've tried Googling "mini PC DDR4 3200" (for example) but the results are meh and trying to find a good deal has been frustrating. Haven't had any luck with either.

I have:
- 32GB (2 16GB sticks) of Crucial DDR4-2400 SODIMM RAM
- 16GB (2 8GB sticks) of Kingston DDR4-3200 SODIMM RAM

Finding RAM to fit systems is easy, but going the other way has been a pain. I'd really like to make use of these. (I have a fair amount of much older RAM that's just gathered dust over the years and seems like a waste.)

Ideally I'd find something like an inexpensive ($300 or less ideally) NUC or an AMD-based mini PC that I can use as a Kubernetes node or to run test database services. These would run Ubuntu, Debian, or RHEL / a RHEL clone. A dual NIC system would be great.

The NVMe drives are less of a pain to match, but the variance in speeds for RAM makes it a bigger pain. I know you can usually get away with, say, putting DDR4-3200 DIMMs into a system that wants slower RAM, but the other way not so much.
posted by jzb to Technology (2 answers total)
I think maybe you're being too specific? You will definitely lose performance trying to use 2400MHz DDR4 in a high-performance system (like something with a Ryzen 5700 or something, or an I7 11700, etc.) but the base speed of DDR4 is 2133MHz. Any system that uses DDR4 can work with RAM down to that speed, and higher spec RAM will often default to 2133 or (sometimes) 2400MHz anyway unless you turn DOCP/XMP on in the BIOS, if your chipset and BIOS support it (which some don't! so you're stuck with the slower speed regardless of what you shove in*). They'll all start there anyway as they figure out what timings to use. So, you're really just looking for a mini PC that uses DDR4 in SODIMM format, which should be most of them. (Only the latest, highest powered things would have DDR5, and anything with DDR3 will be.. pretty old.) It'd be more productive to figure out what you want for CPU and then find the machine from there, and then maybe double-check to make sure the RAM will work in it (if you want, I wouldn't bother with this, especially not for the 3200MHz stuff).

One thing I would double-check on is the storage in the machine, actually - I got a couple of these little crappy Celeron mini PCs to fiddle with (one became my Home Assistant system) and one of them actually has a mini-PCIe slot in it or something. Not an M.2. I was going to drop a cheap NVMe SSD in it but nope, it's stuck with its eMMC storage (unless I want to put a SATA disk in it). This was one of those ones that hovers around the $100 price point, though, so anything much nicer ought to have an actual M.2 slot in it (though, again, that would be worth double-checking to make sure it's not keyed for SATA only).

* This is especially true of the lowest end chipsets, like the AMD A-series (A520, etc.) and the Intel H-series (H610, etc.) - they don't feature any sort of fancy stuff at all so you don't even get DOCP or XMP a lot of the time. I have some 2666 stuff in a H610 board and it doesn't support XMP, so even that little tiny bit of an overclock is lost to me; it runs at 2133MHz.
posted by mrg at 8:22 AM on January 19

Many mini-PCs specifically need low voltage RAM. It's not enough to just know the form factor or speed of this leftover RAM, but also the voltage to ensure some degree of compatibility.

The Intel NUC specifications page lists the specific types of memory each of the various released NUCs will take. In my experience, NUCs generally last forever and are very cheap in the used market, so you might want to flip through the specs from oldest to newest and grab a used one where the specs seem like it will work.
posted by eschatfische at 8:37 AM on January 19

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