Changing the Refresh rate from 7.8 to 3.9 can be VERY important, dependant on the module... the 2400 Transcend 10-13-11 i have, require that, my Gskill 2000 9-9-9 do not, to reach good speeds and timings...tREF does matter too, but it was negligible compared to the first one...having a low TRC...