The DPU-84 Display Processor Unit provides sensor input processing. The DPU-84 is capable of switching the necessary deflection and video signals, and power for the electronic flight displays. The DPU-84 can drive two electronic flight displays with different deflection and video signal for example Electronic Attitude Direction Indicator on one display and an Electronic Horizontal Situation Indicator on the other. The typical 2-tube EFIS-84 system consists of one DPU-84 Display Processor Unit providing the drive signals for two EFD-84 Electronic Flight Displays. The DPU-84 supplies a backup drive for the cross-side electronic flight displays in the event of a failure of the cross-side.

The DPU-84 requires forced-air cooling to be provided. The DPU-84 is capable of operating at short time elevated operating temperatures without forced-air-cooling, however continuous operation at these levels is not considered normal. The DPU-84 provides a high temperature warning output that can drive an external installer-supplied annunciator. This annunciator turns on if the internal temperature of the DPU reaches +100 °C in still air.