An internal combustion engine has a plurality of cylinders, and each cylinder has at least one first and one second exhaust port with associated respective first and second exhaust valves. At least one first and one second exhaust manifold are flow-connected to the respective first and second exhaust ports. A turbo unit for supercharging the charge air delivered to the cylinders comprises at least one first and one second exhaust gas turbine respectively flow connected to the first and the second exhaust manifolds. An exhaust gas chamber flow-connects the first and the second exhaust manifolds upstream of the exhaust gas turbines. The first and second exhaust valves can be deactivated/activated during operation. A throttle valve in the exhaust gas chamber may assume a closed position in order to separate the first and the second exhaust manifolds. A method of operating includes opening and closing different valves at different engine speeds.