Fudzilla: "Intel's slowest of three to launch Lynnfield quad-core CPUs with a dual-channel memory controller will surface at 2.66GHz. Just as any other Lynnfield it has 8MB of memory, but unlike the 2.93GHz Lynnfield, it will have only 4 thread support.
It looks like Intel wants to deliberately slow this CPU down as it should be replacing 2.67GHz Clocked Core 2 Quad 9400. With eight threads we can bet that 2.66GHz Lynnfield makes Core i7 920 clocked at the same speed run for its money and Intel doesn't want this.
The maximal single core clock speed of 2.66GHz quad core Lynnfield is 3.2GHz and this is achieved with Turbo boost mode. There will be a slightly faster model that will support all eight threads and cost a bit more, so better forget about this one."