The Sandy Bridge Preview

A New Socket and New Chipsets

There’s no nice way to put this: Sandy Bridge marks the third new socket Intel will have introduced since 2008. The first was LGA-1366 for the original Nehalem based Core i7. In 2009 we got LGA-1156 for Lynnfield, later updated with support for the dual-core Clarkdale CPUs launched in 2010. Next year, Sandy Bridge will launch with LGA-1155.

The CPU and socket are not compatible with existing motherboards or CPUs. That’s right, if you want to buy Sandy Bridge you’ll need a new motherboard.

As is the case today, there are two lines of chipsets for consumer desktops: H and P series. The H series supports Sandy Bridge’s on-die graphics, while the P series is strictly for discrete graphics.

At launch we’ll have P67 and H67 based motherboards, both of which are in testing right now. A quarter later we’ll see value H61 motherboards added to the mix.

With P67 you lose integrated graphics but you gain the ability to run two PCIe x8 cards off of the CPU. You also get fully unlocked memory multipliers with P67, whereas H67 is locked to whatever official DDR3 speeds Intel supports with Sandy Bridge (currently DDR3-1333).

Both H67 and P67 support 6Gbps SATA, however only on two ports. The remaining 4 SATA ports are 3Gbps. Motherboard manufacturers will color the 6Gbps ports differently to differentiate.

There’s no native USB 3.0 support on these chipsets, but most motherboard makers are looking to third party solutions to enable USB 3 on Sandy Bridge boards.

The other major (and welcome) change is the move to PCIe 2.0 lanes running at 5GT/s. Currently, Intel chipsets support PCIe 2.0 but they only run at 2.5GT/s, which limits them to a maximum of 250MB/s per direction per lane. This is a problem with high bandwidth USB 3.0 and 6Gbps SATA interfaces connected over PCIe x1 slots. With the move to 5GT/s, Intel is at feature parity with AMD’s chipsets and more importantly the bandwidth limits are a lot higher. A single PCIe x1 slot on a P67 motherboard can support up to 500MB/s of bandwidth in each direction (1GB/s bidirectional bandwidth).

With native 6Gbps SATA support, the faster PCIe interface will be useful for any third party USB 3.0 controllers.

Original Nehalem and Gulftown owners have their own socket replacement to look forward to. In the second half of 2011 Intel will replace LGA-1366 with LGA-2011. LGA-2011 adds support for four DDR3 memory channels and the first 6+ core Sandy Bridge processors.