But, it's looking like 28nm Bulk is going to give the stock clocks a considerable haircut - hence the big mystery in terms of actual performance gains. On the face of it, it looks like AMD made some solid improvement to Kaveri B, but their sub par foundry partner may eat up much of AMD's gains.
The Fab Club seems to have intentionally obfuscated the performance advantages of 28nm bulk over 32nm bulk, making the guessing game difficult. It's hard to get an idea of just how bad the hit will be, but we can likely assume that the Fab Club's gate-first 28nm has equal or lower performance than TSMC's gate-last 28nm. Given that TSMC's 28nm is decidely slower than GloFo's 32nm PDSOI, we can safely assume that there will be a noticeable regression in clock speed. Correspondingly, Kaveri's frequencies suffer.
The regression from SOI to bulk for AMD is somewhat comparable to the regression from planar to FinFETs for Intel. Intel's FinFETs only regress at high voltage, while making considerable gains at low voltage, while the loss of SOI should result in a penalty across all operating voltages.
Basically, in a sense, at 28nm (AMD) and 22nm (Intel), enthusiasts have encountered and will continue to encounter frequency regressions while overclocking. AMD's stock clocks will also take a hit.
There's light at the end of the tunnel, though. GloFo moves to gate last with 20nm, which will result in better performance in addition to traditional scaling. On the Intel side of things, the change from planar to FinFETs will only be felt once, and since it's a "true full node improvement," we should once again see maximum operating frequencies, i.e. max overclocks, push forward. Broadwell should overclock at least as well as Sandy Bridge, excluding unforeseen problems. Whatever AMD ends up putting on 20nm should clock very high as well, especially if they move back to SOI.