For future reference and edification: on certain Supermicro motherboards running OSes of Windows 7 or newer (including the Server variants like 2008 R2 or 2012), USB keyboard and mouse devices will act ‘stuttery’ or freeze during input. The issue I encountered was specifically missing keystrokes or repeated letter presses, and appeared to be present even before the OS had booted.
In X9DRW-iF, USB Mouse can’t work under Winodws 7.
Please change “ISOC” setting from disable to enable in the BIOS menu for problem solving. (This item locates at Advanced / Chipset / NB / QPI Config –> ISOC)
To clarify, reboot the server and get into BIOS by pressing Delete at startup when prompted. “NB” refers to North Bridge.