Intel itself says mainstream Core i7 derivatives aren't coming out until the second half of next year, but that apparently hasn't stopped a Chinese website from getting one of the chips and benchmarking it. Expreview has nabbed the benchmark screenshots and posted more details.
The site says Lynnfield will be based on the same Nehalem architecture as the Core i7, and that it will also have four cores, 8MB of L3 cache, and Hyper-Threading technology. However, the chip will have only two channels of DDR3 memory, and it won't feature a QuickPath interface. Instead, it will connect to discrete graphics cards directly via 16 lanes of PCI Express, and it will use a direct memory interface to talk to the chipset.
In benchmarks, the purported 2.13GHz quad-core Lynnfield prototype completed a 1M SuperPI run in 19 seconds and got a multi-threaded score of 12523 in Cinebench R10. For what it's worth, the Core i7-920 scored 16020 and the Core 2 Quad Q9300 hit 10846 in our tests under (presumably) completely different conditions.
According to Expreview, you can expect Lynnfield CPUs to launch in the third quarter of 2009 at less than $200. Judging by photos that leaked out a while back, those chips will have different packages with fewer pins than their Core i7 brethren. Expreview points out that CPU-Z refers to the prototype CPU as a "Core i5," as well.