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Closer Look at LGA1155 Platform

At first glance, Sandy Bridge processors support the same external interfaces as their predecessors, like Clarkdale. They are two DDR3 SDRAM channels, 16 PCI Express 2.0 lanes, FDI-interface connecting the graphics core with the monitors and even a bus connecting CPU with the chipset South Bridge similar to DMI. Despite these similarities, however, the new CPUs should go inside a new LGA1155 processor socket, which is incompatible with the one pin bigger LGA1156 neither on electrical nor on mechanical levels.

LGA1155 CPUs (left), LGA1156 CPUs (right)

Although this transition seems somewhat illogical at first glance, it wasn’t done for marketing reasons. It was required by the radical redesign of the voltage regulator circuitry. It was necessary not only because the new processors are manufactured using “finer” technological process and therefore can work at lower voltages. It is much more important that Sandy Bridge processors support new version of Turbo Boost and use three independent voltages instead of two. The graphics core has now become an independent domain that works at its own frequency and with its own power, and this particular feature allows it to change its operational parameters separately from the cores or even get fully disabled in idle mode.

Migration of current Intel processors from the LGA1156 platform and the need for a new mainboard are definitely not the news you would want to hear. And even the remaining compatibility with existing cooling systems is not going to be a sufficient compensation. It is especially sad that the new LGA1155 chipsets from the “sixth” series do not really excel the previous chipsets in features.

At this point Intel offers two new chipsets for the typical desktop systems on Sandy Bridge platform: P67 and H67. These chipsets are very similar to the P55 and H57, which you can notice from the chipset flow-charts below:

Intel P67 Express chipset

Intel H67 Express chipset

There are two important differences from the predecessors. Firstly, sixth series chipsets support SATA 6 Gbps. Two SATA ports out of six can work at higher speed and it is an extremely timely innovation, since fast SSD with 6 Gbps interface are becoming more and more popular these days. Secondly, new chipsets are finally supporting PCI Express 2.0, so not only graphics cards connected to the processor, but also other controllers (like USB 3.0) will be able to utilize the doubled bandwidth of this bus.

At the same time, P67 and H67 could use their own USB 3.0 controller, so even after the launch of the new LGA1155 platform there is still no chipset in the market with USB 3.0 functionality. The new Intel chipsets no longer support PCI, so the only way to implement this bus on the new mainboards is the same as with USB 3.0: with additional controllers.

The mainboard makers are going to add more new features to the new platform. For example, traditional BIOS will be replaced with UEFI (Unified Extensible Firmware Interface). And this isn’t just a name change, UEFI should solve several problems. It will add native support for 3 TB hard drives, speed up the POST procedure and replace the dull text interface of the BIOS Setup with the more appealing graphics windows.

The differences between P67 and H67 chipsets are quite logical. The first one is targeted for high-performance desktops, while the second one – for systems working with integrated graphics. So, H67 supports two independent monitor outs, but cannot split PCI Express x16 processor bus in two for a pair of graphics cards. Moreover, H67 is missing some enthusiast functionality: this chipset doesn’t support processor overclocking and doesn’t allow using anything faster than DDR3-1333 SDRAM.

Taking into account numerous user requests, Intel is going to add another chipset to their LGA1155 family called Z68. It is going to be a hybrid combining P67 and H67 functionality. It will allow using integrated graphics (like H67) and overclocking the CPU and memory (like P67). Z68 is scheduled to come out in Q2 2011.

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