So I had a look into the pinout of a mPCIe Connector (and the pinout described in the PCIE 2.0 Base Specification). But I am not sure which signals are really mandatory to be used as declared by the description of the "standard" pinout and which pins of the mPCIe Module can just be used for any other signal - while still beeing "compliant" to the mPCIe specification?

In other terms: From a Mini PCIe Card I assume that it uses PCIe as the communication "type" (i.e. PCIe physical layer, data link layer and so on...).But have look at this board (just to have an example):


They claim to be mPCIe standard compliant, but acutally don´t use any PCIe signaling? For example they use UART signals on the lines dedicated for differential transmit pair of PCIe. ?

Can anyone assign any function to egde card of a Mini PCIe Modul and claim that it is standard compliant?

EDIT: I found the follwing phrase in the standard: Two primary data interfaces are defined for PCI Express Mini Card: PCI Express and USB System designers may optionally choose to implement slots that support only one of these interfaces and still be compliant to this specification.

--> So If i interpret this correctly, I have answered my question and was a bit too quick in asking here. But to be sure: That means as long as I use USB signals on the mPCIe connector, I am conform to the PCIe standard, although I don´t use PCIe?


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That means as long as I use USB signals on the mPCIe connector, I am conform to the PCIe standard, although I don´t use PCIe?

Yes, as you are not obligated to implement the full sets of mPCIe connections. A good portion of manufacturers have implemented usb only slots, while another portion tend to have two slots per board, one full and one usb only, due to its convenient connector for internal, modular usb devices (wifi, bluetooth most common).

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    \$\begingroup\$ This is almost correct. Wifi is almost always on the PCI bus. The Bluetooth is always on the USB bus. The reason is the USB Bus only is 2.0 -- you are unable to implement higher speed WiFi on the USB interface. The second Interface in most laptops is connected to a Sata Controller in addition to the PCI bus, but not to USB. This is the reason that you can do Cellular or SSD in that slot, It is also the reason that a half-mini SSD will not work in the wifi slot -- no sata controller there. Some Dell Latttitude's have an additional mPCIe slot that is PCIe only. \$\endgroup\$ Commented Mar 23, 2018 at 11:09
  • \$\begingroup\$ The most annoying part of MiniPCIe is that it is impossible to tell what parts of the spec any vendor implemented without trying a known device in a slot or putting a device in a series of known slots to test the functionality. Some times you only need to go into the BIOS, others you need an Operating System. In Windows you can view the device manager as "Devices by Connection". In Linux variants lspci and lsusb wiil allow you to see the same information. \$\endgroup\$ Commented Mar 23, 2018 at 11:21

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