New Chipset: Intel P55 Express
The launch of Lynnfield processors resulted into serious changes in platforms structure. Since they are positioned solely for single-processor systems they don’t have QPI interface that is also used in LGA1366 systems to connect the processor and the chipset. That is why Core i7-800 and Core i5-700 processors received their own core logic set called Intel P55 Express.
The main peculiarity of this chipset is its simplicity. Nehalem microarchitecture allowed to remove the memory controller from the chipset and now time has come for the PCI Express controller to follow. Since from now on the CPU is responsible for supporting this bus, all functions that have traditionally been performed by the chipset North Bridge have now migrated to the CPU. As a result, there is no need for the North Bridge chip anymore and Intel P55 Express became the first Intel core logic set made of only one single chip – Platform Controller Hub (PCH).
The processor and the chipset in LGA1156 systems are connected with the Digital Media Interface (DMI) bus with 10 Gbps bandwidth in each direction, which used to be employed to connect the chipset North and South Bridges before. That is why the new Lynnfield processors in LGA1156 systems can be used just fine not only with the new Intel P55 Express chipset but also with the old ICH10 South Bridge.
At the same time, we can’t say that P55 PCH is very different in functionality from ICH10. In fact, they simply updated the existing interfaces and extended their number. The following table gives you a better idea of the innovations:
We need 8 PCI Express 2.0 lanes in the P55 chipset in order to ensure that additional devices can also be connected to the platform besides the graphics cards. The CPU in LGA1156 systems can only provide connection with the PCI Express graphics cards and the P55 PCH is responsible for supporting other devices. In fact, we saw almost the same implementation in X58 Express, where the chipset North Bridge was only responsible for work with graphics cards. An important improvement in P55 Express was the introduction of PCI Express 2.0 bus support. It means that devices supporting this specification can exchange data with the chipset twice as fast as they used to before.
Moreover, the USB controller has also been changed. It doesn’t support new or faster protocol versions, but delivers more ports. Besides, it also allows hardware disabling of individual ports, which is valuable for security purposes.
Mainboard makers have prepared a lot of solutions on Intel P55 Express by the LGA1156 processors launch. As an example of a platform like that we would like to offer Intel’s own offering – DP55KG mainboard – and point out some of its primary architectural peculiarities.
In fact, besides the presence of only one core logic chip, we also notice immediately that it is topped with a pretty “weak” heatsink, which has nothing in common with those sophisticated solutions usually offered by the manufacturers of the enthusiast mainboards. However, Intel didn’t try to save some money here, because P55 Express PCH simply doesn’t need any state of the art cooling. Even though it is manufactured with 65 nm process, its typical heat dissipation is only 4.7 W. For example, the typical heat dissipation of the X58 Express North Bridge is 24.1 W. That is why those mainboard makers who will still use massive chipset cooling systems on their products, will simply increase the cost of their solutions without any reason and thus mislead the users.
The second peculiarity of the LGA1156 platform is the simplified processor socket design. Compared with LGA1366, the processor retention mechanism is fastened to the mainboard with three screws instead of four, and the lock is catching on to one of the screws and doesn’t require an additional metal frame around the socket. However, this is barely a serious modification: they must be simply trying to save some metal here.
I would also like to mention the design of the second PCI Express graphics card slot. Since in case of a dual-card configuration it will only work in 8x mode, Intel removed its second half, which can anyway serve only aesthetic purposes under any circumstances.