As with all of the Vault hardware, the FW4 series need only RAM (memory) and mSATA (storage) added in order to have a fully functional hardware system. In addition, an optional WiFi module can be installed as well. For more information on HW compatibility, see this link.
The annotated photo below shows the location of the various sockets.
The FW4 Series uses an Intel Atom E3845U processor (located on the underside of the motherboard). This CPU has built in suport for Intel’s AES-NI hardware encryption.
There is a single SODIMM socket for memory. Additional information on compatible memory modules can be found in the Hardware Compatibility page.
The FW4 series comes with a single mSATA socket.
The WiFi module socket is a PCIe form factor socket.
Note that the wifi module, while PCIe in form factor, operates over USB channel communication, limiting functionality as compared to pure PCIe modules. Protectli sells a compatible wifi module that is available here.