Let's see how this "worse performance" looks like depending on CPU load, considering SMT would account for about +25% IPC increase and taking 6c/6t as the base for relative performance increase:
- Until 6 threads both 8c/8t and 6c/12t will perform at almost identical performance levels with a 6c/6t, including power usage.
- At 7 threads the 8c/8t will offer 16% more performance and the 6c/12t will bring +4% over 6c/6t.
- At 8 threads the 8c/8t will be at +33% , the 6c/12t will offer +8%.
- At 10 threads the 6c/12t will jump at 16% relative advantage, still considerably behind the 33% advantage of the "inferior" 8c/8t.
- It takes 12 threads for the 6c/12t to hit it's max throughtput of +25%, and with the help of somewhat smaller power usage at full load come out even or slightly on top of the 8c/8t.
While some may argue SMT offers a bit more power efficiency than extra raw cores - leading to higher clocks , this will only happen in scenarios where thread count well past 8, more likely 10-12.
Moral of the story? SMT needs higher thread count to truly shine. Physical cores kick in faster.
Ask Intel, they've been doing this kind of wasting for many years now.
If that were true, then consumer would have nothing to gain from a 6c/12t chip either. Everything above 4c/8t simply doesn't make any sense, high clocked Intel 4/8 chips also beat lower clocked 6/12 chips.