Intel PM55 Express Chipset
If you read our recent coverage of the Lynnfield processor (Intel Core i5 and the Core i7 800-series), then the diagram below of the Clarksfield platform should look very familiar (in fact, it is the same diagram). As we previously mentioned, Clarksfield and Lynnfield have the identical architecture. The same can be said for the P55 and PM55 chipset feature sets.
Prior to the release of Lynnfield and Clarksfield, the Core i7's PCI Express interconnects were still located on the chipset; therefore the Intel X58 chipset for Bloomfield processors still required a Northbridge chip and a speedy QPI interconnect between the processor and the Northbridge chip. Now with the PCI Express interconnects and the memory controller located on the processor die, the Northbridge chip is gone from the equation and the CPU communicates directly with the Southbridge chip via a DMI interconnect.
The PM55 chipset supports up to 14 USB 2.0 ports and six SATA 3Gb/sec ports; it also supports Intel Matrix Storage Technology RAID support and Intel High Definition Audio. The PM55 chipset also includes support for up to eight PCI Express x1 ports. PCI Express ports 1 through 4 can be configured as either four x1, two x2, or one x4 lane groups; the same is true for PCI Express ports 5 through 8. This means that the PM55's PCI Express lanes could be configured as two x4. Unfortunately, it is not possible to gang all eight PCI Express lanes into single x8 skit.