Expreview claims the upcoming Core i5 "Lynnfield" processor from Intel will feature a higher BCLK frequency and lower QPI multiplier than the Core i7 processors. One of the implications of this is that the Core i5 will be less ideal for overclocking than the Core i7s.
As we know, QPI restricts the CPU’s overclocking performance. Take the Core i7 965 as an example, it comes with 6.4GT/s QPI data rate, 24x multiplier and 133MHz BCLK. Due to the limit of QPI speed (8GT/s), its maximum BCLK can only achieve 166MHz at 24x.
But according to our source, the QPI multiplier of Core i5 will be set lower at 16x, so you’ll get a higher BCLK around 250MHz. When you overclock the BCLK, the QPI interface will overclock as well.