Originally posted by: IntelUser2000
The exact reason is they are starting to exhaust single thread performance increaing options.
Back when Core 2 Duo first came and Johan said Free Lunch is Back:
http://www.anandtech.com/showdoc.aspx?i=2748&p=6
"The result was that the reputed Dr. Dobbs journal headlined : "the free lunch is over" [1] claiming that only larger caches would increase IPC a little bit and that the days that developers could count on the ever increasing clockspeeds and IPC efficiency of newer CPU to run code faster were numbered."
Core 2 didn't use new ideas to increase single thread performance. It refined known ideas and expanded on them. Excellent prefetchers, Memory Disambiguation, better prefetcher, 4-issue, these aren't new ideas. There is no free lunch after all.
Turbo Mode was implemented because taking advantage of extra TDP headroom when running cool or not running all the cores is a good idea when implemented well. Clock speeds increase performance uniformly, unlike other architectural changes.
The next Tock, Sandy Bridge is only enhancing the Turbo Mode further:
http://en.wikipedia.org/wiki/S...ge_(microarchitecture)
"Dynamic Turbo allows the CPU power to exceed the TDP value when the rest of the platform is relatively cool. The frequency gain can be up to 37% for one minute, and over 20% in most cases."
10-15% performance single thread gain will come from clock speeds.