The C2 stepping removes the VT-d bug in C1 CPUs, which affected the CPU's hardware accelerated virtualization support.
While C1 CPUs are only running the software-accelerated only mode, the C2 now properly supports hardware acceleration on a hosted OS, Intel said. According to the document sent out on December 9, samples of the C2 Sandy Bridge-E processors became available last week. Commercial retail and tray units will begin shipping on January 20.
Intel told its customers that it does not anticipate "change to customer platforms designed to Intel guidelines." However, if a customer chooses to enable Intel VT-d, "regression testing is recommended to ensure their board is properly enabled," the PCN states. Those customers who prefer their own BIOS will have to install the latest Microcode update to support the C2 stepping.