I am networking a 999HD SI and 859HD DI along with an IPilot link on my new boat. I finally located a 5 port ethernet switch which will arrive tomorrow, so in waiting, wanted to update the software on the 859. Humminbird says both units need to run 6.900 to be able to share the side, and down imaging. I loaded the 6.900 on my sd card, but the 859 would not recognize the new software. I tried two different cards, loaded after restoring defaults, and also on startup, with no luck. Do the units have to be networked, and see each other, before the 859 will allow the 6.900 update? Thanks in advance!