Intel Lynnfield Core i5-750 & Core i7-870 Processor Review

P55 Express Chipset Examined

Intel's new P55 Express 'Ibex Peak' chipset is a true break from their traditional chipset design. Unlike all previous Intel chipsets which featured both a northbridge and a southbridge (eg. X58 Express + ICH10R), the P55 is a one-chip solution. As such, it has been given the new designation of Platform Controller Hub (PCH). When it comes to PCI-Express 2.0 connectivity things get a little complicated with this chipset since in the past, the northbridge supplied the graphics-related PCI-E lanes. However, Lynnfield processors feature an industry-first: an integrated PCI-E controller that supports 16 PCI-E 2.0 lanes supplying two mechanical PCI-E x16 slots. If only one graphics card is installed, it will operate at the full electrical x16 speed and if two graphics cards are installed, the PCI-E lanes are divided between both PCI-E x16 slots and they will operate at x8 each. On motherboards with three mechanical PCI-E x16 slots, the first two slots will each operate at x8 while the third slot will operate at x4. How is this possible if we have already established that the integrated PCI-E controller only supports 16 PCI-E lanes? The additional 4 PCI-E lanes come from the P55 PCH itself, which can supply up to 8 PCI-E 1.0 lanes in total.

On the connectivity front, the P55 supports 14 USB 2.0 ports and 6 SATA II ports with Matrix Storage Technology. It also features one Gigabit LAN port and HD Audio Technology. It does not feature support for Intel's Trusted Execution Technology (TXT), formerly known as LaGrande, which provides hardware-level protection against malicious software.

The P55 PCH communicates to the processor via the Direct Media Interface (DMI), which is a 2 GB/s point-to-point connection, which is roughly equivalent to a PCI-E x4 1.0 link. By the way, the DMI is by no means new, it has long been used as the link between the northbridge and southbridge.

Much like the P45 Express and X58 Express chipsets, the P55 PCH is manufactured on the venerable 65nm process, and it has a low default voltage of 1.0V. As a result of this low voltage, and the simple fact that the P55 does not actually do much, it does run quite cool. Did we mention that it is also relatively tiny? The P55 package size of just 27mm x 27mm, and the actual die is a minuscule 8mm x 8mm as revealed below:


Next let's see what kind of motherboards Intel themselves have built around this new chipset.