Just to check try the two modules in DDR3_2 and 4 instead.
it show me 2 channel
i try put 2 ram on DDR3_2 and 4 it show me same problem.
i read from G.Skill Forums that P55 board from Gigabyte has the problem with compatible untill Gigabyte release a new bios to fix the bug.
could it be the same problem?
Dual Channel Memory Configurations:Channel 0: DDR3_1, DDR3_2
Channel 1: DDR3_3, DDR3_4