I too have a crippling dual CPU workstation hoarding habit. Single thread performance is usually worse than enthusiast consumer desktops, and gaming performance will suffer if the game isn't constrained to a single NUMA domain that also happens to have the GPU being used by that game.

On the other hand, seeing >1TiB RAM in htop always makes my day happier.

Any pointers on how to buy one?

Personally I use eBay and find the most barebones system I can, then populate the CPU+RAM with components salvaged from e-wasted servers. There are risks with this, as I've had to return more than one badly-bent workstation that was packed poorly.

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So the Dell Precision T7920 runs dual Intel Scalable (Skylake) and has oodles of DIMM slots (24!), but you'll need to use a PCIe adapter to run an NVMe drive. FlexBays give you hot-swappable SATA, SAS too but only if you're lucky enough to find a system with an HBA (or add one yourself). But if you manage to salvage 24x 64GB DDR4 DIMMs, you'll have a system with a terabyte-and-a-half of ECC RAM - just expect to deal with a very long initial POST and a lot of blink codes when you encounter bad sticks. The power supply is proprietary, but can be swapped from the outside.

The T7820 is the single-CPU version, and has only 6 DIMM slots. But it is more amenable to gaming (one NUMA domain), and I have gifted a couple to friends.

If you're feeling cheap and are okay with the previous generation, the Haswell/Broadwell-based T7910 is also serviceable - but expect to rename the UEFI image to boot Linux from NVMe, and it's much less power efficient if you don't pick an E5 v4 revision CPU. I used a fully-loaded T7910 as a BYOD workstation at a previous job, worked great as a test environment.

Lenovo ThinkStation P920 Tower has fewer DIMM slots (16) than the T7920, but has on-motherboard m.2 NVMe connectors and three full 5.25" bays. I loaded one with Linux Mint for my mother's business, she runs the last non-cloud version QuickBooks in a beefy network-isolated Windows VM and it works great for that. Another friend runs one of these with Proxmox as a homelab-in-a-box.

The HP Z6 G4 is also a thing, though I personally haven't played with one yet. I do use a salvaged HP Z440 workstation with a modest 256GB RAM (don't forget the memory cooler!) and a 3090 as my ersatz kitchen table AI server.

    >and a lot of blink codes when you encounter bad sticks

Which sadly happens quite a lot with ECC DDR4 for whatever reason.

    >If you're feeling cheap and are okay with the previous generation, the Haswell/Broadwell-based T7910 is also serviceable

The T5810 is a known machine, very tinkerable, just works with NVMe adapters (they show up as a normal NVMe boot option in UEFI) and even have TPM 2.0 (!!!) after a BIOS update. Overall, they are the 2nd best affordable Haswell-EP workstations after the HP Z440 in my opinion.

    >E5 v4 revision CPU

They are less efficient than V3 CPUs due to the lockdown of Turbo Boost, but then again on a Precision you'd have to flash the BIOS with an external flasher regardless to get TB back.

Forgot about Dell gimping Turbo Boost on that firmware.

Another route is the PowerEdge T440 (tower server), which does respect Broadwell-EP turbo logic without a reflash. Not quite as quiet as a workstation, though.

It's not an issue with Dell it's an issue with how the chips themselves are designed. There are buggy microcodes in the Haswell-EP series which can be exploited to unlock FULL Turbo Boost on ALL cores of the CPUs. This is NOT possible on Broawdwell-EP.

Man this so much incredible information in one comment

Power usage is the main limitation of using these as a home server. They have a high idle power use.

One of the reasons I use these is because it’s cold half the year and it’s not hard to basically use to supplement the heat.

The CPU is far less powerful than a single Ryzen chip from now and the new system is far more power efficient. No super fast USB connections like a new system has.(It does have a USB-C 10GB connection though) Overall if you can live with a bit older machine, it's pretty decent.

Very bad performance per watt and higher maintenance needs. Bad performance per watt generally means a larger formfactor and more noise as well.

I bought a Dell Precision 7910 2x Xeon E5-2687W v3 (10 cores, 20 threads each) with 32GB RAM and 512GB SSD for $425 including shipping. I found that Windows 11 Pro will recognize only 20 of the virtual cores/threads. I don't feel a need to upgrade to more expensive Microsoft OSs at this time, so I just run Ubuntu natively on that box, which recognizes all of it. Assuming used DDR4 RAM returns to more reasonable prices at some point, I intend to load that box up to the 768GB max.

On Dell you'll probably be stuck with the original mobo, and their SFFs don't take standard PSUs

In favor of their SFFs, they get retired 10k at a time, so you might as well pick up a second one for spares.

Not a bad call, although you'll probably need to upgrade the PSU to add a GPU (if you can find one small enough to fit the SFF case)

Just performance when compared to current generation hardware. Not significantly worse, but things like DDR4 ram and single thread performance show the signs of aging. Frankly for similar $$$ you can get a new hardware from beelink or equivalent.

Got it so basically it's one of those things you do if 1) the project interests you and/or 2) you get one dirt cheap and don't have high expectations for certain tasks