D0 Processor Stepping: a Little Bit of Theory
Intel usually warns their closest partners about any changes in their products architecture or functionality. The same happened with the new processor stepping: they sent out the corresponding informational bulletin back in January 2009. Although, it was not too informative and told pretty much the following about the new stepping:
«The electrical, mechanical and thermal specifications remain within the current specifications. Intel anticipates no changes to customer platforms designed to previous Intel guidelines».
In other words, Intel engineers didn’t promise any evolutionary changes in the features of their processors based on the new core. However, Intel’s official claims about the identity of different processor steppings is barely a good argument for computer enthusiasts. According to our practical experience, even minor enhancements of the processor core may sometimes result into a noticeable practical improvement of heat dissipation, power consumption and overclockability. That is why experienced users always try to get their hands on processors featuring the latest core revisions. Especially, since in our particular case it is not that hard to distinguish between the CPUs on D0 processor stepping from their predecessors. Besides the core, Intel will also change one of the marking elements.
Also, Core i7 processors with new D0 processor stepping receive a new CPUID classifier that will now be equal 0x000106A5 (instead 0x000106A4 for the previous generation CPUs with C0 processor stepping). Therefore, to ensure correct operation of the new processors, mainboard manufacturers will have to update their BIOS code and include the support for the new core version into it. Luckily, the leading mainboard manufacturers have already done it, so you shouldn’t worry about compatibility issues.
Due to new CPUID, diagnostic utilities recognize the new processor core correctly. For example, here is the screenshot from the CPU-Z utility for our Core i7-975 XE:
Note that so far D0 processor stepping exists only in two types of Core i7 processors: the latest mass production Core i7-920 (new CPUs have SLBEJ S-Spec) and in Core i7-975 Extreme Edition engineering samples that are not retailing yet.