Quote Originally Posted by JF-AMD View Post
Let me put it in simple terms:

With actual cores, throughput generally goes up ~90% when you go from 1 core to 2 cores.

With SMT, throughput generally goes up ~14% for int and ~20% for FP (from SPEC.org, on Intel-based submissions).

SMT may double the number of threads, but it does not double the number of pipelines. You can only fit so many executions per cycle based on the pipelines. SMT might give you better utilization, but you are still limited on pipelines.

Doubling the number of cores will double the number pipelines and allow for more simultaneous execution. That is the key to this whole discussion. Everyone can argue about how many angels can dance on the head of a pin, but in reality, having more cores means that you have a larger dancefloor.
The advantage of SMT is that it doesn't need a lot of extra chip area. While an extra core will take a lot of chip area.