According to Intel's Product Change Notification 111286-00, the X79 Express Chipset will be transitioning to a new C-1 stepping in April 2012. The document suggests that the changes implemented in the C-1 stepping will be detailed in the Intel X79 Express Chipset Component Datasheet, but as of today that document has not yet been updated.
Source
I also extend due credit to a post by nightmare99 at overclockers.co.uk.
Quote:
Description of Change to the Customer:
The Intel® X79 Express Chipset is converting from the C-0 stepping to the C-1 stepping. Please plan to validate the C-1 stepping of the Intel® X79 Express Chipset. For technical details of the Intel® X79 Express Chipset, please refer to the component Data Sheet and latest Specification Update available on CDI and/or intel.com product support web site.
Customer Impact of Change and Recommended Action:
The C-0 stepping of the Intel® X79 Express Chipset is pin-to-pin compatible with the C-1 stepping and does not require any motherboard modifications. Design changes, however, have been made to the IOH component of the Intel® X79 Express Chipset and will require customers to perform re-qualification. Please see the Intel® X79 Express Chipset component Data Sheet and latest Specification Update and the Intel® X79 Express Chipset BIOS Specification Update for any BIOS changes available for the C-1 stepping.
The Intel® X79 Express Chipset is converting from the C-0 stepping to the C-1 stepping. Please plan to validate the C-1 stepping of the Intel® X79 Express Chipset. For technical details of the Intel® X79 Express Chipset, please refer to the component Data Sheet and latest Specification Update available on CDI and/or intel.com product support web site.
Customer Impact of Change and Recommended Action:
The C-0 stepping of the Intel® X79 Express Chipset is pin-to-pin compatible with the C-1 stepping and does not require any motherboard modifications. Design changes, however, have been made to the IOH component of the Intel® X79 Express Chipset and will require customers to perform re-qualification. Please see the Intel® X79 Express Chipset component Data Sheet and latest Specification Update and the Intel® X79 Express Chipset BIOS Specification Update for any BIOS changes available for the C-1 stepping.
Source
I also extend due credit to a post by nightmare99 at overclockers.co.uk.
