Check out the supported firmware versions listed for each system after selecting ESXi 6.0 (assuming you are going to the latest version) ... this is as close as "documented" as you'll find. [URL] Firmware updates aren't going to change the compatibility. If you are worried, check the release notes for red flags. 
 Hi All,   I am planning to upgrade firmware on my two Dell servers.   Now my manager want like an official paper or website which says that the upgraded firmware will be supported by the ESXi software.  That is if after the upgrade of the firmware BIOS/network card etc, this will be supported by the ESXI version.     The servers are already in production.    Can any one direct me to the site where I can verified the compatibility of firmware against ESXi software please   Thx Regards Nicolas  
Upgrade firmware on esxi servers