i have saber tooth z77 motherboard with a ivy bridge i5 and kingston hyper x ram. the fan runs when the ram is out of my computer, but once i remove it the fan does not spin fully, it only gives a slow quarter turn
With no RAM modules in I expect it isn't posting so will just run the fans at a full power state. What do you have the fans set to in the BIOS? there is a monitoring section and you should be able to set a minimum speed etc.