Were you aware that you can use it on ALL units, even those without the software update?
You just have to put the map on the card differently for the depthfinder to recognize it. I had been using autochart on my 788ci HD for two months now, and it does not have the autochart update yet. They just released a software update for that unit on July 31st.
http://www.humminbird.com/Category/Support/FAQ/AutoChartUseW_O_SoftwareUpdate/But, to answer your question, I believe it is any unit with software version 6.90 or newer, has the autochart features added.
Autochart support has been added through software updates for some 600's, 700's, 800's, 900's, 1100's, ION & ONIX units.