Our new to us boat has master and slave (using manufacturer terminology) Northstar 6100i units. Slave on bridge turns on but does not show anything so we scored a craigslist replacement that works, however the new slave has software updated that the original master does not. As far as I can tell I download the software update onto my computer from here: Downloads for Northstar 6100i | Northstar Then I use something like this to transfer it to a CF card like this: https://www.amazon.com/SanDisk-Comp...pID=41LN-4viTpL&preST=_SX300_QL70_&dpSrc=srch Using something like this: https://www.amazon.com/Compact-WEme...pID=41lVe7pQUGL&preST=_SY300_QL70_&dpSrc=srch Then I insert that CF disk with the software update files into the chart reader on the 6100i unit(s) following instructions in the downloaded files. For anyone familiar with updating a Northstar unit, does that all make sense? Any other suggestions? This fancy electronics is all new to us. Thanks in advance for any input.