Does all M.2 slot support 5G modem?

I am looking to buy
However, it doesn't have any sim slot.

The suggested solution is to get

I thought that should solve the problem, however this comment reminded me and made me a bit concern, A board with M2 but doesn't have any sim slot. What are possible solutions? - #5 by AndrewZ

I remember that I read somewhere the usb 2.0 interface is required for the 5G modem to work.
(I think it has something to do with the AT command??? Not an expert on this)

I am looking to buy this modem (RM520N-GL),

I am wondering if anyone knows if the device from aliexpress works with 5G modem?

I think my question is more like "does all M.2 slot support 5G modem?"

From what I have read on wikipedia, as long as it is B key or E key, it has usb line.

B Key provides PCIe ×2, SATA USB 2.0 and 3.0, audio, UIM, HSIC, SSIC, I2C and SMBus
E key provides 2 of PCIe ×1, USB 2.0, I2C, SDIO, UART, PCM and CNVi

Am I correct on this?


Dunno about the PCIe, but you probably want USB 3.0 speed for a 5G modem. <- alternative modem ?


Short answer, no.
Long story short, M.2 B Key slot standard, support Pcie, usb3 and the connection for the sim slot.
Pcie version depends on the soc/cpu, there can be m.2 with pcie 4.0, if it is supported by the cpu, but on iot devices, it is pretty rare.
the Pcie part is 2 lines, 3.0 or 4.0 or whatever, and all 5G modules have 1/2 lines Pcie 3.0, or newer 4.0, and USB 3.0 or higher connections.
This is the standard, so pcie 2 lines, usb 3.0 minimum, and Sim connection.
The truth is, almost all device you can find around, have only 1 type of connection, Pcie, or USB. Devices with both connections are still pretty rare, and costly.
Also, Pcie connection, require MHI driver, so need linux kernel 5.15 or higher to work properly, unless you have a backported driver on an older linux kernel.
In the near future, there will be more devices with standard connections, but as of now, to be compatible with a 5G modem, you need a M.2 B Key slot with usb 3.0 link and sim link, so the device should have a sim slot.
Also, need a decent soc to be able to sustain high speed, and a good power supply on the slot, to sustain the power needs of a 5G module, to avoid throttle, or stability problems. Also it needs a good dissipation.
So, there are many requirements, to classify a board good for 5G, just having an M.2 B Key slot doesn't qualify for 5G compatibility.


E Key is for WiFi Modules, not 5G Modules, the slot is different. Also lack Sim connection, so you can't use it. As for M.2 B Key without sim, you could use an adapter with sim slot integrated.

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Thanks. This modem supports e-sim only. It is a great find for those who doesn't need an actual sim.

Thanks. This is a very detail explanation. It answers many of my questions. Thanks again.

One more question, what is the usb interface for?
Does the M.2 5G modem use the usb interface from the M.2 B key slot to transfer data?
(The data here I mean data from internet. The data usage that occur from using 5G to access the internet.)

Lol, the fact is more complex.
Cellular Modems, are real modems, just like old dial up modems, wich used serial connection.
USB is a serial connection, just to say one.
Upon that, modem switched from a serial connection, to a modern tunnel protocols, wich include multiple type of connections on a single link.
Main Protocols are MBIM, old QMI, and a few others, but linux wise QMI and MBIM are common ones.
They create a serial link, a USB to ethernet tunnel, so that the modem data link appear like an Ethernet adapter, and is used to transmit data,and based on the protocol, QMI or MBMI commands link, to send commands to the modem.
The same thing can be done using PCIE, using MBIM protocol and MHI driver under linux, or RNDIS under windows.
So the modem expose multiple links, using tunnel protocol under USB or PCIE connection.
And this because a serial connection can use only PtP protocol, wich would cap around 30 mbit or so speedwise, while mbim and qmi doesn't have any cap protocol wise.
The speed is limited only by the connection itself, so usb 3.0 4,2 gbit or so, including overhead.
PCIE depends on the version, but can reach 10 gbit with 3.0, PCIE 4.0 could reach double that and even more.
PCIE speeds are example, since it's not implemented on many devices yet, but is used to get higher speed with less problems than usb, and offer a better reliable connection theoretically, because the whole point is making a virtual ethernet adapter out of a serial modem.
If you need more info, you can google MBIM QMI, and overall, how a modern cellular modem works nowaday.


Stiel, thanks a lot.

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