If you setup Performance Enhancement (something like MCE), this removes TDP limits and XFR2 can even auto overclock above 4.3 on single core and above 4.1 on all cores.
Useful tip! Haven't looked into much yet but I've got a good water setup on top of a VERY good air setup so the rads are pretty much breathing ambient/delta+5c_max air. Shortly going to 480mm (though shared with a 980ti).
I'll start looking at that.
So how does the single core boast work? I thought it was just for single thread. But say I'm running bf1 is that classed as lightly threaded? And what does lightly threaded mean? That one core is stacked and just little bits off loaded to the rest?
Just trying to work out if I need to over clock or not
Under XFR1 (X370 etc) it would apply a higher speed to a pair of cores on the fly, if a 3rd was needed, would then IMMEDIATELY drop all cores to sub 4ghz.
Under XFR2 (X470 etc) it will try and work inside a (I think) user set voltage/thermal envelope, if cores are loaded, it'll try and boost them but keep the level of the other cores sensible to make best use of the envelope provided.
That was my take on it in laymans.
So... allowing it to push the small number of cores hard when needed rather than them all being stuck at 4.2/3 all cores may well be beneficial (even more so than overclocking).