Except he's asking about X58 boards, not P67. The X58 UD3 does do SLI. I've got one sat next to me.Sorry mate the P67A-UD3 does NOT do Sli. They do Crossfire. For there to be Sli a NF200 chip is needed.
http://www.gigabyte.com/products/product-page.aspx?pid=3698#ov
And to compare the UD3 board range.
http://www.gigabyte.com/products/comparison/list.aspx?ck=2&pids=3767,3766,3765,3764,3763
Except he's asking about X58 boards, not P67. The X58 UD3 does do SLI. I've got one sat next to me.