So all! After successfully delidding a pair of x5680 and upgrading my Mac Pro 4,1 2.26Ghz 8 core to an absolute powerhouse 5,1 wth dual 3.33Ghz 12 core I got the upgrade bug. After the EFI flash it showed only 1066mhz with my 24Gb triple channel 1333Mhz ram. I bought 96gb of 1333Mhz ECC Registered ram (6x16gb) but it is still only reading at 1066Mhz. Does anyone know why this could be? PS Next upgrades will be the video card and a PCIe SSD !