Since Intel's Lynnfield can run up to eight cores in Hyperthreading, Intel has figured out how to distinguish Lynnfield Core i7 branded SKUs from Core i5.

The logic is very simple. Core i7 has four cores and eight threads enabled, while Core i5 has four cores and four threads enabled.

They both need discrete graphics as Intel 5 series chipset don’t have any IGP as IGP is now part of Clarkdale CPU. However some desktop Clarkdale IGP CPU with 32nm dual-core and four threads inside will end up with Core i5 brand, just to make things a bit more complicated.

All of these CPUs will need a P55 chipset at beginning until the other chipsets from 5 series come along.