An industrial computing device includes a field mountable primary housing having a removable side cover to facilitate expansion. Within the primary housing there is a head board having a processor on one side. On the opposite side, there is an expansion connector adapted to receive an expansion board and at least one peripheral connector, which is coupled to the processor within the housing. The peripheral connector receives at least one PCMCIA card such that the PCMCIA card is also within the housing when plugged into the peripheral connector. The expansion board includes at least one more peripheral connector to receive at least one more PCMCIA card. The peripheral connector, the expansion connector and the side cover are oriented orthogonal to a mounting plane of the computing device. The primary housing can also include a removable front cover, which together with a top or bottom portion of the primary housing, provides an aperture for flush-mounting an I/O device in the form of an internal dongle. The dongle can include a rear cable that connects to the PCMCIA card or other device within the housing, a front connector for coupling to a field device, and a circuit coupling the connector and the cable.