QUOTE(terradrive @ Mar 20 2014, 02:00 PM)
For 290 and 290X, actually there are stock clock speeds. I remembered 290's stock clock is 662MHz. AMD just lists the max boost clock, the reason is that on alot of cases it did manage to hit that speed...
If you see the original msrp price for 290 and 290X, AMD offered the performance based on the price, not based on the max boost clocks. It's just that many people think it's a waste to leave the untapped performance.
I liked the AMD's new powertune 2.0 philosophy in design, just that many people misunderstood how AMD wanted it to work.
But there are often times when it didn't consistently hit either, its bane is mainly due to the lackluster reference cooling solution. If you've run a reference card before, you can easily see how throttled it can become at times. I have tested 3 runs of Heaven and I observed that the overall framerates drop consistently with each subsequent round of testing, especially when once it hit the max thermal threshold. Pricing wise, I believe AMD hit the nail right on the head. That's why today you see massive price cuts on the GTX 770 / 780, and forced Nvidia to unleash the 780 Ti in a desperate grasp to hold on to the performance crown.
Just my own opinion, I believe it was more of a marketing reason to list the max boost clock speed instead of the base clock. People who are more attuned to graphic cards will likely know how the cards perform, but to the less informed, they will easily compare with Nvidia and ask; eh, how come my clock speed just 662 MHz? Nowadays more and more cards are breaking the GHz barrier, so you can guess why things happen as they are right now.

Just an analogy only, I know Nvidia's 780 / 780 Ti all also run at sub GHz clockspeeds also.