''In 2nd and 4th slots from the cpu?
Nothing is wrong, everything is working as it should.
DDR (Double Data Rate) RAM is designed to transfer data twice per clock cycle.
600Mhz x 2 transfers per clock = 1200Mhz effective.
Your DDR3 is working as it should. ''
From another thread, so i suppose its showing half because its transfer twice per clock cycle?