I just installed an X5650 (950-> L5639-> X5650) on a Gigabyte X58A-UD3-r v2, firmware FH, with 12GB RAM (6 x 2GB).
Running at 191 bclk for 22x (4.2 Ghz) on all cores and 23x on 1-2 cores (in Win7; OS X Mavericks only seems to give me all-core multis: 12x, 21x, 22x... odd).
VCore: 1.2125v...