Lynnfield represents something that is both new and old. Its origins are in Nehalem and the way that core architecture is laid out. However, there are some differences. I am not going to go into them in great detail; after all you really want to know how well it performs, so here is a short and quick list of the major differences.
One of the main differences is Dual Channel vs. Triple Channel memory support. On the surface this might not seem like a big deal and for every day computing, you would be correct. This is one of the reasons it could be safely removed for Lynnfield and its mainstream market position.
The new Lynnfield has some performance improvements, too. According to Intel it is roughly 20% faster than the Core 2 Quad when comparing the i5 750 to the Core 2 Quad Q9400. It also represents a 40% reduction is silicone real-estate due to the shift to a 2-chip design.
The reduction is due to Intel moving the control for up to two discrete PCI-e GPUs (one GPU at x16 or two at X8 each) onto the CPU rather than inside the chipset.
We mentioned the reduction in memory channels, but with the loss of one channel comes increased official memory support. Lynnfield now officially supports DDR3-1333. This is a little faster than the DDR3-1066 support for the Core i7 9xx series.
Another reduction is also price. The i7 870, which is the top end 1156 CPU runs only $555 in lots of 1000. This is about half the price of the i7 975, while the P55 boards should also be significantly less making the whole platform more affordable.
This may bite into AMD's Price/Performance line, of course that is only if Lynnfield can perform. So let's find out if it can.