Flawed logic. Try your math again. Your numbers are not correct. Uh, let's start with 93.75-83.33....reversing the math give 151+%.
I look at it this way... we added 33% more cores, but got 50% more performance. that leaves 17% extra performance, spread across 16 cores...
I see your logic as interpreting the increase from only those extra 4 cores....
I've got to agree with Steevo and his math on this one, well since it's right...
Just clarifying his numbers using the 1000 threads per second example
33% more cores: so 12 cores * 1.333333..... = 16 cores
50% more performance: 1000 * 1.5 = 1500 threads per second
So the old 12 core proc. would do 1000 threads per second while the new 16 core will do 1500 per second (threads of whatever, not relavent here... just some AMD spec'd performance numbers):
that means old did 1000/12=83.33 threads per second per core
new will do 1500/16=93.75 threads per second per core
so that's 93.75 for the new and 83.33 for the old. To find the percentage increase that's 93.75/83.33=12.5% faster per core than the old architecture.
Now I'm not sure if AMD's numbers are skewed and that 50% performance increase was more than likely on a specific test; however, going by those numbers they posted the math shows the new cores should be 12.5% faster per clock.