There may still be a FAQ page for each software version on the Humminbird web site. I haven't looked for any older ones lately. I'm not at work today so I don't know if there were any additional software versions for your 798cXi HD Si unit in between 6.740 and 7.120. If there were there should have been either a web page (if it was for more than one model unit and/or software version like the link you posted) or the description was in your My Humminbird account when you went to download the software.