1. Download the latest firmware package here: http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=21517. Extract it to a USB key and run startup.nsh from EFI shell. Note that the USB key must be formatted in FAT or FAT32 partition.
2. Go to Advanced => Processor Configuration menu in BIOS and try to disable "Processor C3" and "Processor C6". You may also try to disable "Enhanced Intel SpeedStep Tech".