What Else Is An M.2 WiFi Slot Good For?

Many mainboards and laptops these days come with a range of M.2 slots, with only a subset capable of NVME SSDs, and often a stubby one keyed for ‘WiFi’ cards. Or that’s what those are generally intended to be used for, but as [Peter Brockie] found out when pilfering sites like AliExpress, is that you can get a lot of alternate expansion cards for those slots that have nothing to do with WiFi.

Why this should be no surprise to anyone who knows about the M.2 interface is because each ‘key’ type specifies one or more electrical interfaces that are available on that particular M.2 slot. For slots intended to be used with NVME SSDs, you see M-keying, that makes 4 lanes of PCIe available. The so-called ‘WiFi slots’ on many mainboards are keyed usually for A/E, which means two lanes of PCIe, USB 2.0, I2C and a few other, rather low-level interfaces. What this means is that you can hook up any PCIe or or USB (2.0) peripheral to these slots, as long as the bandwidth is sufficient.

What [Peter] found includes adapter cards that add Ethernet (1 Gb, 2.5 Gb), USB 2.0 ports, SIM card (wireless adapter?), an SFP fiber-based networking adapter, multiple M.2 to 2+ SATA port adapters, tensor accelerator chips (NPUs) and even a full-blown M.2 to x16 PCIe slot adapter. The nice thing about this is that if you do not care about using WiFi with a system, but you do have one of those ports lounging about uselessly, you could put it to work for Ethernet, SFP, SATA or other purposes, or just for hooking up internal USB devices.

Clearly this isn’t a market that has gone unexploited for very long, with a bright outlook for one’s self-designed M.2 cards. Who doesn’t want an FPGA device snuggled in a PCIe x2 slot to tinker with?

(Thanks to [RebootLoop] for the tip!)

21 thoughts on “What Else Is An M.2 WiFi Slot Good For?

    1. The 2.5g card rj45 mount seems to be designed to fit/mount in a serial port hole or plate. I have one installed in my Lenovo tiny m710q and mounted it in the serial port hole and fits perfectly!

        1. Macgyver24x7, got mine from AliExpress, it’s based on RTL8125B… Make sure you get the one with the 90 degree turn on the ribbon cable pins so it sits flat. I use Ubuntu server and used awesometic dkms driver package to get it to work well. Throughput about 2.4gbits both ways.

          1. Thanks Philip. I plan to pick up a Lenovo tiny M920q pretty soon and plan to install Proxmox on it and transfer all my VMs to it. I think it has an existing Wifi card that I might plan on testing with pfSense. I have an existing dual-port Intel NIC PCIe card, but I need to find a PCIe 90 degree? riser card to see if I nan get it to fit in it. I’ve heard that certain Intel NICs just behave better (than Realtek/etc) in situations like this. I guess I’ll find out. The M920q I’ve spotted also looks like its does have an open serial or VGA port. So if the PCIe option doesn’t work out, I may investigate the M.2 route like you’ve got going. Cheers!

  1. I haven’t had any laptop with this new of technology. But I do remember having laptops with electrically-standard slots inside but a BIOS hack that would only turn the slot on if it recognized the device in the slot as being one of a small number of over-priced WiFi cards that the laptop manufacturer had a stake in.

    Are they still pulling that kind of crap? Might someone get excited about the prospects of what they could add to their laptops and buy accessories only to discover the laptop manufacturer doesn’t allow it?

    1. Last I checked, 10 years ago, HP was still doing this crap. But you are correct, people need to be careful that they don’t have one of these laptops before putting too much effort into this.

      1. I hope that sort of block only affects laptops. I just ordered an A+E to SATA adapter for my reburb HP ProDesk USFF box. I never even knew they existed til today. Thanks Maya of HaD!!

    2. I’ve seen the same sort of thing – though I’d not always say its anything to do with who owns the peripheral company to make money – as this annoyance has all been in the very corporate laptop world as far I am aware. The world where security and reliability are what the company buying your machines is paying you for – so only working off the whitelist and keeping the entire fleet within a few permitted specifications actually makes sense at the time for both parties.

      Its just annoying to the rest of us later if it can’t be turned off on the retired computers…

  2. I assume that the demands of high speed busses have made modern gear shockingly tolerant; but I can’t help but get a little nervous seeing that ribbon cable connecting the SPF cage to the m.2 card. Not a surprise; those things have been cheap and common at least since they were still attaching floppy drives; but I very much associate them with low speed work, like connecting motherboard serial headers to externally accessible ports; and I’m old enough to remember when ATA ditched 40-pin cables for 80 pin because UDMA/66 couldn’t take the crosstalk.

    I’m not surprised that you can get away with it; but it sure doesn’t fill me with warm and fuzzies.

    1. I expect there is some black magic going on in the trace layouts etc to really make it work well for the high speed lines, as these high speed connections are defiantly more challenging. But when you can extend a PCI-E slot at least a few meters with good quality extension cables and have it just work I’d be surprised if over such short distance if it is much of a problem and everything else on the M.2 ‘wifi’ keyings are very slow interface (by todays standards anyway), so should be fine.

    1. Go on Amazon.com and do a search for terms like m.2 to hardware serial cable adapter and PCIE to hardware serial cable adapter and perhaps even thunderbolt to hardware serial cable adapter. For some reason, Amazon and AliExpress seem to be the easiest places for me to find these lesser known adapters. I have seen adapters for serial ports on Amazon. Usually to equip a more modern machine with multiple serial ports through a single adapter, but I didn’t look at their details.
      Unfortunately the serial port specification changed over time, so you want to try and make sure that the one you buy will support your hardware. For example, sometime around the late 1990’s or 2000 the requirement to supply power for an external device was removed. So a lot of computers and adapters made since the change will not work with devices that were designed to draw power off the port. They usually still work with very low power devices like keyboards and mice, even older ones, but not necessarily other things unless they have their own power input.
      If you can’t find what you need there, I would try Crowdsupply.com and GitHub to see if anyone has a project that does what you need.
      Best of luck!

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