I have a Gigabyte GA-MA790XT-UD4P board and 2 out of the 4 ram slots work. Slots 1 and 3 work and 2 and 4 don't. I know it's not the ram because I can switch the stick into the working slots and it boots into windows. When I put the ram into the problem slots it doesn't even show the post screen it just sits there, I guess turning on and off I can tell this because of my graphics cards fan. I reset my cmos and left my computer unplugged overnight but it still has the problem.