An off chip driving system includes a decision circuit, multiple first and second adjustable-enhancement circuits, and multiple first and second drivers. The decision circuit outputs a first and a second decision signal according to a clock and an input data. Each first adjustable-enhancement circuit generates one of first control signals in response to the first and the second decision signal and one of first optional signals. Each second adjustable-enhancement circuit generates one of second control signals in response to the first and the second decision signal and one of second optional signals. Each first driver is coupled to the corresponding first adjustable-enhancement circuit and configured to be enabled in response to the corresponding first control signal. Each second driver is coupled to the corresponding second adjustable-enhancement circuit and configured to be enabled in response to the corresponding second control signal.