Official BIOS for UD3R,
Yes, after confrimed the BIOS with nvidia and Gigabyte,
GA-EX58-UD3R offically supports SLI technology.
and you just need to upgrade BIOS from website.

link is here,

http://www.gigabyte.com.tw/Support/...=2989#anchor_os

BIOS: F5 2009/03/30

1. Support nVidia SLI

also, after F5, all BIOS including Beta BIOS all supports SLI.