A plasma arc system includes a single-gas, gas-cooled plasma arc torch and a torch control unit. The torch control unit includes a housing and a user input device on the housing for receiving an indication of a desired cutting or marking function and for providing a responsive signal. A single gas supply both to the housing, and from the housing to the torch, is provided for cutting or marking. A current control device is located within the housing for controlling current output to the torch for either cutting or marking. A gas control device is located within the housing for controlling gas output to the torch for either cutting or marking. A controller is located within the housing for receiving the signal from the user input device indicating the desired cutting or marking function, and for sending a responsive signal to the current control and gas control devices depending on the desired cutting or marking function so that the torch operates accordingly. A related control until is disclosed.