The HDAWG-SKW Output Skew Control option enhances the skew control resolution of the HDAWG's signal outputs to a value of 10 ps. In comparison, the skew control resolution of the base HDAWG instrument is a single sample clock cycle, i.e., 417 ps at the maximum sampling rate of 2.4 GHz. High-resolution skew control is relevant for some applications that require simultaneous sub-nanosecond signal rise times and inter-channel skew calibration below the nanosecond level.
Note: In many cases, it is possible to achieve sub-sample precision in the timing of the output signals without the hardware change offered by the HDAWG-SKW option. See this blog post to learn how to adjust the timing of an output signal to a resolution much finer than the sampling rate.