The P55 PCH, Unveiled
In the preceding picture, you probably noticed that there's only one chipset component on the P7P55 Evo PCB. Of course, this is because much of the functionality previously housed by the memory controller hub (in the Core 2 days) now resides on the CPU package itself.
Core i7 saw the memory controller make its way into the processor, leaving Intel's X58 to handle PCI Express connectivity. Core i5 sees even that base function migrate northward into the processor, charging P55 with the capabilities once reserved for Intel's family of I/O Controller Hubs. In an effort to try differentiating, however, P55 is now being called a PCH, or Platform Controller Hub.
The PCH you see here is revision B1 silicon, which is still considered buggy. B2 will fix some of the board's existing USB compatibility issues, we hear.