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Use TB3 M.2 PCIe NVMe enclosure as basis for custom box for regular PCIe AICs?


I was unable to find a OOB product that suits my requirements:

A small box with a PCIe 3.0 x4 interface to use regular non-GPU PCIe AICs with computers with a Thunderbolt 3 port. The first use would be an Intel XL710 2 x 40 GbE ethernet adapter (natively PCIe 3.0 x8, but am fine. with it being limited through TB3).

Can I DIY-build such a thingy with an external enclosure for M.2 PCIe NVMe SSDs and actively powered M.2-to-PCIe adapters?

Example of such an enclosure:

I’m asking since I don’t know if there are any limitations to TB3 that the manufacturer can specify so that it can only be used for NVMe devices…?

Thanks for the input!

As I’ve experienced, getting the boot sequence correct on a Thunderbolt device is neigh impossible. This is a bad idea to begin with using Thunderbolt 3. Using U.2 to relocate a AIC is much better solution. Since it’s raw PCI-E though, make sure it’s shielded and short.

The USB 3.0 cable based solutions are all typically x1 which won’t work if bandwidth is a concern.

The clarify for a normie: Why is the boot sequence relevant for an ethernet adapter (not using to boot off of network)?

I wanted to make such a “box” to be able to get stuff faster to/from laptops and a desktop computer that has TB3 but no more PCIe lanes available.

But do I understand you correctly that there shouldn’t be a reason why this shouldn’t work by design?

Why I asked this question:

Experience with a non-TB3 ASUS Pro WS X570-Ace motherboard:

  • Motherboard has a built-in U.2 port (from X570 chipset) that can be switched between (PCIe, UEFI default) and SATA (option))

  • PCIe NVMe SSDs work fine on that interface with PCIe 3.0 x4 link

  • Now I wanted to use this port to attach a regular PCIe AIC with such an adapter

  • Devices in the adapter don’t show up at all

  • On the other hand: I can use M.2-to-U.2 adapters and a chain of PCIe AIC-to-M.2 slot, M.2-to-U.2 adapter, U.2-U2 cable and the first adapter mentioned above to operate regular AICs
    (with both, PCIe lanes coming from the CPU and from the X570 chipset)

Don’t understand it.

Dedicated U.2 ports seem to act weird and only accept NVMe devices. Using adapters seems to be the better bet.

A little saaad that 4 PCIe lanes get “wasted” this way :frowning:

Yeah, it’s quirks like that, which I’m finding out doing Thunderbolt devices, now knowing not everything is equal. U.2 on a motherboard can restrict it to NVMe Protocol only. Same with NVMe enclosures for Thunderbolt 3, in that the controller only accepts NVMe Protocol and not PCI-E.

Best bet is adapters. Take a M.2 Port, turn it into U.2, then turn that U.2 into PCI-E. This is the best bet since there’s no special treatment of those lanes like with onboard motherboard U.2 ports.

Is there such a thing like a “simple” TB3 -> neutral PCIe slot adapter thingy?

You still have the PCI bridges (The Thunderbolt controller itself) and boot initialization issues to deal with there. If you send PCI-E signals down a U.2 cable similar to a riser, this is not an issue.