Form what I have been told there are no Si or 2D sonar changes with the 4.570 or 4.620 software updates. In fact I don’t know what they changed other than some internal manufacturing testing stuff. That’s why there has been nothing announced about them.
The 4.260 software for the 981/987 is old and I’m not sure why it was not put on the Humminbird site last year when it was released…
Before anyone asks: I don’t know when the TVG (now to be called “Switchfire”) updates will be released for the 981/987 or other units. Nor do I know when the newer 2010 changes will be available either. Last I heard was what Mark Gibson said at iCast which I believe was the end of September but don’t quote me on that as my audio went on my work PC again so all I can do is see his lips move when I watched the video again!