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First off, you're absolutely right. The difference in IPC between a modern CPU and a 2002 vintage Pentium 4 is pretty incredible, and the way forward is all about power efficiency and cramming more cores onto one die. However, I think it's unfair to say clock speed is an unfortunate marketing gimmick "anymore" when it was a gimmick all the way back in 2002 when Intel released the 3.06 GHz "Northwood" Pentium 4 that the OP's linked article references. In fact, it was a gimmick that caused one of the biggest strategy/roadmap blunders Intel ever made. Intel designed NetBurst (the architecture that the P4 was based on) to do one thing really well: allow Intel to ramp up clock speeds quickly. The architectural choices they made to enable this severely hobbled the P4's performance, especially the 20 (later 31!) stage pipeline that made the penalty for branch mispredictions pretty awful. Intel eventually released P4s that clocked as high as 3.8 GHz and had an unheard of (in the x86 space) 115 watt TDP, but when the Athlon 64 was released, AMD could smoke Intel's fastest P4s using slower clocked CPUs with lower TDPs. Instead of focusing on raw clock speed, AMD focused on architectural improvements like x86-64, HyperTransport, and an integrated memory controller. (Intel CPUs wouldn't see QPI or an integrated memory controller until Nehalem, released five years after the first Athlon 64.) As you say, the tables are now turned — clock for clock, the IPC of AMD's Piledriver core is behind that of even Intel's (two generations old) Sandy Bridge core, and all AMD seems to be able to do is add more cores and crank up the clock speed. Unfortunately for AMD, adding more cores doesn't help single-threaded performance, and a very nasty side-effect of increasing clock speed is that the processor's TDP increases disproportionately: the 4.7 GHz FX-9590 has a whopping 220 watt TDP, while the 4.0 GHz FX-8350's TDP is 125 watts. |