A review of Intel's single-core Pentium 4 670, which runs at 3.8GHz with 2MB of L2 cache, has been published by SimHQ:

The 6xx series of processors are based on the Prescott core, manufactured with Intel's 90nm process, run on an 800MHz front-side bus, and launch out of the production chute with 2 MB of L2 cache. As noted in SimHQ's P4 660 review, the 6xx series bears striking resemblance to Intel's Extreme Edition processors in terms of cache size, transistor count (169m), and supported features, though the latter runs on the faster 1066MHz front-side bus.



Link: SimHQ