Why FXBeam for the Expansion Bay connector?

Curiosity’s gotten the better of me and I’ve been wondering… Why would Framework choose FXBeam for the Expansion Bay connector? I really like how the Expansion Cards use a standard USB-C connector and having the Expansion Bay also use a standard connector would be really cool. PCIe or OCP NIC would probably take up too much space but maybe OCulink 8i and Micro-Fit BMI single row? This way it’s easier to source parts for DIY and users don’t have to remove the keyboard and keep track of 4 screws when switching out the module.

There isn’t just PCIe on that connector so it would have to be a modified standard, and please find me a connector that can handle 200W (12V at 20A). Micro-fit is a wire to board along with Oculink. Those types of connectors will increase the thickness of the entire chassis but with this approach you can still keep it relatively thin along with reducing the expansion bay PCB BOM by one part

Have fun with signal integrity without screws.


The current design of the expansion bay connector has 184 pins because it not only supplies PCIex8 but also a lot of power in both directions, PWM for fans, USB and DisplayPort signal.

USB-C has 24 pins. Oculink has 42 or 80 pins depending on the size. Theoretical you could combine a USB-C port plus an oculink port plus a display port plus some custom solution to deliver the power, but this would create a mess of plugs and probably create a fragile and unreliable connection.

I think it’s pretty clear that Framework isn’t trying to create a hotplugable solution, but more something like the PCIe sockets in desktop PCs.

Someone will surely try to hotplug this :smiley:

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Yeah, those were just examples. Reducing BOM is always good!

My main concern was if someone were to make their own DIY module they wouldn’t be able to get the connectors because those look custom but then I realized the connector is literally just ribbon cables (that Framework could sell if spares are needed!) and then said DIYer would just need to put some pads on the PCB… D’oh!

Oof, I didn’t even think of that! Now that I am thinking, having to take it apart a bit to unscrew the connectors has a neat side effect of providing a way to deter it.

[edited for clarity]

Yes, or you could repurpose them from the laptop or from existing expansion bay modules. That’s kinda the advantage, you just need some pads and holes (although for a proper contact, the pads probably should be gold plated, which could be expensive for DIY).

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As far as I know PCIe is in general capable of being hotpluged but only very few cards and mainboards are capable of it. Additionally you need OS and driver support for that. Just randomly pulling out a GPU and inserting a new one probably won’t work and could damage the card as well as the mainboard if they aren’t explicitly designed for it.

Not sure on what level Thunderbolt handles that, since I can hotplug my eGPU (while the GPU itself is most likely not hotplug capable) and it even has a “safely remove” option in Windows.

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