The release notes list some important fixes to memory and CPU speed stepping features. See Dell BIOS Release Notes.
Corrected an issue where turbo mode was not being engaged when in
Maximum Performance Mode
Our ESXi hosts are hosted in a lights out datacenter, so we wanted to do these updates remotely.
As @DuncanYB wrote in his Dell Firmware Update post, the task of updating Dell BIOS and Firmware is often fraught with pitfalls and missteps - just reading the 50+ comments made me realize this might be challenging - but the comments pointed me to this promising post:
I was able to setup the Dell Repository Manager (DRM), and use it to create an ISO, boot the R610 remotely from the ISO using our Avocent virtual media, and it applied a bunch of firmware updates for 20 minutes, but the BIOS on next boot still showed 2.x!
So what I ended up doing was using cobbler to PXE boot the R610 to a Dell OMSA LiveCD - allowing me to scp the BIOS_NV3N8_LN32_6.1.0.BIN linux bios runtime file and apply successfully.