here is a list of all bios (stable and beta release) for X58 UT: http://www.mediafire.com/?43a05mjr9o6ve

D615 bios date should be 6/15/2010

p.s. in the link above there are some modded bioses, I've tested only D615MOD and it shows errors during post.
DON'T FLASH THEM if you doesn't have a bios programmer or another eprom.