I'm planning on upgrading my 7936 conference phones' firmware to the latest version, 3.3(20). The download page notes that the compatible Call Manager versions are 4.1, 4.2, and 4.3. I'm running Call Manager Express version 3.4(0). How do I know if the new conference phone firmware will be compatible with my CME?
CME compatibility info is here : http://www.cisco.com/en/US/products/sw/voicesw/ps4625/products_device_support_tables_list.html
Basically click on a document that says 'Cisco Unified CME 8.0 Supported Firmware....' for your CME version; it then lists your 'supported/tested' firmware. Generally I would start with whatever is on this list for a given version of CME, and only upgrade if you have a particular problem or know of a common problem with that firmware.