Keysight M9703A Series Configuration And Measurement Instructions page 9

Keysight M9703A Hardware Extension of 89600 VSA Software
Force Software DDC
This function overrides the hardware processing which is normally performed by the
M9703A, and forces the VSA software to perform the DDC operation. It is provided
simply as a demonstration of the difference in performance between hardware DDC
and software.
It can be enable as shown in the screen capture below by ticking the Force Software
DDC option.
M9703A Hardware Extension of 89600 VSA Software 9