Why does the geforce 8600 have a faster core clock than the 8800?

The core clock is similar to RPM's in an engine and is only part of how fast it is.

A 50cc scooter may have really high RPM's on a small engine and the result is it doesn't go very fast. A big V8 may not have as many RPM's but can go very quickly.

The same for the video cards. The 8600 may have a faster clock but has fewer pipelines to do the work. The 8800 may have a slower clock but has way more pipelines to do the work.

Result: The 8800 is a much faster processor.

Clock rates are not important if the processor has more pipelines / a better instruction set.

Which would you rather have: a 3.4 Ghz Pentium 4, or a 2.8 Ghz Core 2 Duo?