The DS-9664NI-M8 is an improved version of the DS-9664NI-M8 with various improvements such as more processing power and more cool features.
Read much more about it - and everything else - on the product page for the new version: DS-9664NI-M8
We have kept the product page for the DS-9664NI-M8 so that you always have easy access to the documentation.