A solid state disk drive is provided among the storage devices controlled by a storage controller. Communications information is received at a first DMA gateway of a DMA gateway communications network. The first time period and the second time period is compared, and any one of the first both-sides image forming processing and the second both-sides image forming processing is selected based on the comparison. A micro mechanism is located at a lower position to increase the electro-static discharge. A contact plug may be electrically connected to the active region and spaced apart from the word line, and a bit line may be electrically connected to the active region through the contact plug with the plurality of bit lines extending in the first direction.