The connection between the electronic processing units driving the EFBs and the respective displays is 1000Base-SX, a 1-gigabit/sec fiber optic link accommodating digital video. Each electronics unit comprises a pair of computers–partitioned off from each other–one running a Part 25-certifiable version of the Linux operating system and the other running Windows 2000. Each of the four computers contains a 40-gigabyte, sealed hard drive pressurized to 1 atmosphere to prevent a disc crash during rapid decompression. The Linux operating system, where the Level D applications reside, controls the display and allows reset of the Windows partition in flight.