Another nice feature with these units is that you can update the software with the sd cards. You just have to register at humminbird.com and then you can download the updates for free. Then you just copy the file to the sd card, put it into the unit and turn the power on, the unit will see the new software and ask if you want to update.
My matrix 37 was updatable, but I needed to use the PC connection package from humminbird and the humminbird pc program(free). It’s a lot nicer using the sd card, I don’t even have to take my 987 off the boat