M.2 Slot in Phone

On Todd Weaver’s recent Reddit AMA, he said that the modem in the phone will be in an M.2 socket. See https://www.reddit.com/r/IAmA/comments/87tbfl/todd_weaver_from_purism_doing_a_reddit_ama/dwfh9nb/?st=jfiqa5hg&sh=df3e76c8 for more info.
Will it be possible to remove the modem and put in an SSD or other compatible M.2 piece of hardware? If so that is extremely exciting.


follow-up question here: if this is possible to swap in an SSD for the modem, I’m guessing we can remove the ssd from our Librem laptops and pop them in our phones for on the go productivity?

M.2 has different ‘keying’ for drives vs wifi/bt, so they are not interchangeable (So sadly what you want to do is not physically possible). https://en.wikipedia.org/wiki/M.2#/media/File:M2_Edge_Connector_Keying.svg


Thank you for the info!

Are you sure? Which key dose the wwan card has? I thinlk there are 4g modem cards with the B key out there (siera EM7565) which supports the usb 3 interface used by this card. But for B keys there are also sata ssd available, maybe even pcie ones with just 2 lanes. Which interface are you intend to connect to the m.2 slot anyways or do you have to provide all interface specified for a key?

I even think wwan and gnss modules are supossed to use the b key which is also intended for ssds. Or am i mistaken that the modem should go into the m.2 slot. Because wifi is already on the chip isn’t it. Or do you want to us 2 m.2 slot a wifi and a wwan one?

Just curious, why M.2 and not mPCIe? The latter would have made the board potentially only as thick as the PCB + SMT components instead of that plus a fixed-height screw post. Plus, mPCIe just clips into place whereas M.2 requires a screw which can easily be misplaced. Seems like mPCIe is a better fit (in more ways than one) for the mobile phone use-case. Am I wrong in this assessment?

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The socket for the card will always be taller than a screw post, because the screw post only needs to reach the underside of the card, while the socket has to extend above the topside of the card. (Unless it hangs over the edge of the main board.)

But in any case, mPCIe has pretty much the same basic physical design as M.2, except that mPCIe (Mini PCI Express) cards are larger and have holes for two screws. (But usually only one screw is fitted.)

Perhaps you are thinking of the earlier Mini PCI cards, which do use a clip in mechanism, like memory modules. However, Mini PCI cards are obsolete and about twice the size of mPCIe cards and close to thrice the size of some M.2 cards.

Only Purism can answer this but perhaps part of the motivation was the potential need to bring the audio in on dedicated pins (rather than via USB). (I believe that using actual PCIe lanes is ruled out for security/privacy reasons.)

In any case at the end of the day, Purism is limited by suitable modem cards. If the modem card is M.2 then that’s what the slot needs to be. Given the current market size of the Librem 5, you can’t expect much market clout to get modem card manufacturers to do what Purism wants.