The paper studies two implementations of an observer-based output feedback controller designed to control a third-order single-input single-output linear plant. The first controller is a direct implementation of the observer equations, requiring two inputs. The second controller is an equivalent cascade version of the observer-based controller, requiring only one input. The cancellation of the observer poles which appear as common factors in the numerator and denominator of the cascade controller transfer function yields annth-order controller. The plant is simulated on an EAI 680 analogue computer and the controllers are implemented digitally on an Intel 2920 microprocessor in the feedback loop and forward loop, respectively. The performances of the two digital controllers are compared.