Intel is launching a new CPU socket called LGA1156 with a new chipset, P55. The first three CPUs based on this new platform will be Core i5-750 (2.66 GHz), Core i7-860 (2.80 GHz) and Core i7-870 (2.93 GHz), all based on the new “Lynnfield” core. We had the pleasure to receive a Core i5-750 and a Core i7-870 sample from Intel before their launch, so let’s take a look at their performance compared to other CPUs from Intel.
As you may be aware, Intel is adopting new names for their CPU families. Core i3 will be the family targeted to entry-level PCs, Core i5 will be the family targeted to mid-range PCs and Core i7 is the family targeted to high-end PCs. Core i3 products were not announced yet and Core i5-750 that we are reviewing today will be the first Core i5 CPU to be launched.
Some Core i7 processors based on a core called “Bloomfield” were already launched (Core i7-920, Core i7-940, Core i7-950, Core i7-965 and Core i7-975), but using a different socket, LGA1336.
Core i3, Core i5 and Core i7 processors have an integrated memory controller, just like CPUs from AMD have since the very first Athlon 64 (launched in 2003). The memory controller from the models released so far accepts only DDR3 memories, with socket LGA1366 CPUs supporting triple-channel configuration and socket LGA1156 CPUs supporting dual-channel configuration. This is one of the main difference between socket LGA1156 and socket LGA1366. This way, socket LGA1366 is targeted to high-end PCs only.
Under dual channel configuration, two memory modules are accessed at the same time. This doubles the available bandwidth compared when we had only one memory being accessed at a time (single channel). So on PCs using dual-channel configuration memory modules must be installed in pairs so the system can achieve its maximum performance. On triple-channel architecture, three memory modules are accessed at the same time, increasing the available bandwidth by 50% if compared to a dual-channel configuration running at the same clock rate. Thus in systems using Core i7-9xx you must install memory modules in multiples of three in order to achieve the maximum performance the CPU can deliver.
As you can see, it is easy to tell which socket a given Core i7 CPU is based. Models targeted to the new socket LGA1156 start with the number eight, while models targeted to the socket LGA1366 start with the number nine.
Another difference between the “old” socket LGA1366 Core i7 and the new socket LGA1156 Core i7 and Core i5 is that Core i7 processors already launched (Core i7-920, Core i7-940, Core i7-950, Core i7-965 and Core i7-975) officially support DDR3 memories up to DDR3-1066/PC3-8500, while the new socket LGA1156 CPUs support DDR3 memories up to DDR3-1333/PC3-10600.
On the pictured below we compare the physical differences between sockets 775, 1156 and 1366.