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LGA1156 Platform Evolution

Clarkdale processors that come to replace Core 2 family solutions send the entire LGA775 platform to the garbage heap of history. Being the bearer of Nehalem microarchitecture, Clarkdale doesn’t use FSB processor bus, but has a built-in North bridge like Bloomfield and Lynnfield. Intel decided not to introduce a new processor socket form-factor for Clarkdale and designed it compatible with LGA1156 platform, which obviously turns into a practically universal solution at this point. As a result, Clarkdale, just like the previously launched LGA1156 Lynnfield CPUs, has the same set of functional units (computational cores, L3 cache, memory controller, PCI Express controller) and employs DMI bus to connect to the chipset South Bridge.

In fact, Intel winds up the evolution of their platforms by launching the new Clarkdale today. As a result of this evolution, the chipset has completely lost its traditional role: North Bridge has become a part of the CPU and there is only one chip left from the chipset – the South Bridge, which is responsible for interfaces for external devices. Therefore, any contemporary system now consists of only two primary chips instead of three.

When Intel developers were making sure that Clarkdale complied with the new platform building principles, they had to take another revolutionary step. The thing is that since Clarkdale is targeted for the mainstream and low-end segments, there must be a platform option that would use an integrated graphics core. As you remember, graphics cores used to be integrated into the chipset North Bridge before, but it no longer exists as an independent functional unit. As a result, the graphics core followed in the footsteps of the memory and PCI Express bus controller and also moved into the processor. So, Clarkdale became one of the first desktop CPUs featuring not only computational units but also a GPU.

I have to say that although Clarkdale has an integrated graphics core, it doesn’t have to be used in all systems. The CPU also features a PCI Express x16 graphics bus controller, which means that Clarkdale based systems can also take on discrete graphics cards. In this case the integrated GPU will be disabled. The systems built on mobile Clarkdale modifications called Arrandale will also offer some choices when it comes to interaction between the graphics core integrated into the processor and the add-on graphics card. For example, you will be able to switch between the internal and external graphics core without rebooting the system. However, desktop platforms won’t support this function.

You must use special chipsets for Clarkdale processor to be able to employ the integrated graphics core. They are called Intel H55 Express, Intel H57 Express and Intel Q57 Express. The primary difference between them and the already existing Intel P55 Express LGA1156 chipset is in the special digital interface aka Intel FDI (Flexible Display Interface). It is intended for transferring the video signal from the processor through LGA1156 socket outside to HDMI, DVI or D-Sub mainboard outputs. However, it is implemented in a very simple manner: FDI bus uses DisplayPort and chipsets supporting integrated graphics have a small controller in their South Bridge that provides routing and digital-analogue conversion of the video signal.

As a result, different LGA1156 processors and mainboards appear mutually compatible, despite obvious differences between them. Clarkdale processors can work with an external graphics accelerator in any LGA1156 mainboards based on the old Intel P55 Express as well as the new Intel H55, H57 and Q57 chipsets. However, if you intend to use the integrated graphics core, you can only go with solutions on Intel H55, H57 and Q57 chipsets supporting FDI and featuring “monitor” outs on the connector panel. BY the way, the existing Lynnfield processors are also compatible with these new boards built around Intel H55, H57 and Q57 chipsets, but you will have to use an external graphics card, because these processors have no integrated GPU.

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The ability to use the integrated graphics core in the CPU is not the only difference between the LGA1156 chipsets. Intel P55 solution that doesn’t support FDI bus is the only chipset that allows using a pair of graphics cards connected as PCI Express 8x + 8x. Intel H55 targeted for entry-level systems doesn’t support RAID and features 12 USB 2.0 ports instead of 14 alongside with fewer PCI Express lanes for peripheral devices. The Q57 chipset targeted for corporate systems supports Intel AMT remote system management technology. Intel H57 is the most feature-rich modification supporting integrated GPU.

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