I think it was enabling Internal PLL Overvoltage, but I wish I knew what it really did. I couldn't boot even at like 1.38 before without this setting enabled... after I enabled it I could boot at 1.34.
Not so sure about the CPU PLL. I was playing with it last night and found interesting stuff.
My temp goes UP when I make the CPU PLL LOWER than 1.832.
It passes the test (used quick LinX w/AVX all ram) fine with 1.750.
But it gives me 3c higher in temp.
I though I was doing something wrong so I went back to 1.832 and test it and did the 1.750 again.
But the results are the same. (I tested it 3 times back and forth)
1.832 runs cooler than 1.750.
Weird but that is what I got and also I get better score at 1.832 (133+GFlops) opposed to 1.750 (131~2GFlops).
Optimal VTT/VCCIO for me was actually not 1.1, but 1.077. 1.051 (my stock) was pretty good and a bit better than 1.1v as suggested, but in the end 1.077 was just much better. It took a lot of testing and to be honest I cant say that these findings are 100% correct because of the nature of stability testing (ie you can never be 100% certain), but I had very improved results. Right now I'm about to go lower my vcore and see if things still work.
PLL lets you reach very high multipliers when overclock (like 48+)

if you couldnt boot with 45x, but can with pll, then i guess you just need it a little bit sooner than most

that vtt shouldnt make a difference
What do these do precisely? I read something that suggested PLL Overvoltage if enabled allows higher voltages to be delivered to the core, as if it is some sort of limiter on the max voltage (i.e., regardless of your BIOS Vcore settings). Is that true, slightly off or completely off?

Is it some sort of protection mechanism around 1.38v because 1.38v is what the max recommended/safe/whatever voltage is?

With both of these adjusted -- PLL Overvoltage enabled and VTT I raised to 1.1v -- I am having a lot better results. I'm just trying to understand what these do, particularly the VTT voltage, so if I find instability I know which to change. Obviously I'm kind of on the right path now... previously without these settings I couldn't boot regardless of my Vcore.
PLL lets you reach very high multipliers when overclock (like 48+)

if you couldnt boot with 45x, but can with pll, then i guess you just need it a little bit sooner than most

that vtt shouldnt make a difference
PLL Overvoltage, not PLL voltage.