Epic questions. I can do a few.
1/ Yes. Higher multiplier at lower bsck is going to perform worse than higher bsck at the same clock. The difference might not be deemed significant but it is definitely there. The appeal to the extreme editions as I see it is running a bsck of 200, which is within the normal motherboard limits of 220 or so, and then whatever multiplier you can get to. You can also kill the dirty mess that is turbo, since you don't need that extra +1 multi. Something like 200x25 would be the one I'd shoot for, but you're not getting that on air and probably not on water.
2/. Most people take the vid range as safe. Up to 1.375V for you. I am scathing of this, just because Intel say they'll sell a chip which runs at this voltage does not mean it is the limit or that it is safe. Stock voltage depends on chip, I'd expect around 1.1V or so. Stock ram voltage is 1.5V, that's almost certainly going up to 1.66V (1.65V if the board lets you pick this). However you've asked what's safe.
A safe voltage is one which does not cause measurable deterioration during the lifespan of the product. However what is safe is a function of temperature. 1.5V at -50 degrees is probably fine, 1.5V at 120 degrees is likely to kill it. It depends on what you're cooling it with. Most people on air seem to be at 1.3V or lower, otherwise they cannot control the temperatures. I don't know what I'll run on, probably whatever keeps the processor below about 80 degrees or when I hit diminishing returns. Currently 1.2 or so for 4ghz [ I'm having temperature issues with the motherboard, so am going to have to cool that more competently before pushing further. I hope you're aiming fans at the mosfets.] It's personal choice really. I'm going to push mine relatively hard, because I think processors are harder than people give credit for. However I will
not use load line calibration, were I doing so I'd set am much lower safe voltage. llc causes spikes of far above what is set in the bios and generally makes bugger all sense, it's also violating intels voltage supply regulations. All you get is the peace of mind of the voltage not going down with load.
3/ Pretty certain if you just change multi, everything else stays the same. QPI is probably going to need more voltage, its the analogue of P45 northbridge voltage. So more qpi voltage when clocks go up, when ram is pushed harder etc. I'm unsure as to what is considered safe, but as its on processor die putting it up makes things hotter, and a cold processor can probably take a lot more on the qpi.
4/Yes. I'm disabling it on a 920 because I don't want the board changing the multiplier around. Were I using speed step I'd be more inclined to have it on. However you have an extreme chip, so have whatever multiplier you want without messing around with turbo. Definitely turn it off.
5/I had this argument with someone a while ago. I agree with you. 2000mhz is only usable at higher bsck than 133. The person who'd bought it refused to overclock and thought it was unreasonable that his ram was running below stock. The main issue is that you hit problems around the ucore > 4000 mark where stability just goes to hell. The limit depends on chip and probably on temperature, and imposes a general restriction on how high you can push bsck or ram. Hence I run 1600mhz ram, there's one multiplier lower to fall back on if needed and otherwise 200 x 20 @ 1600mhz ram are just really nice numbers for 24/7 if I can't get any higher.
Intel say the ram voltage cant go over 1.65V or you'll hurt the processor. The ram companies are a bit close lipped but I think are of the opinion that their ram will be fine well over this. Several people running at 1.7, a few at 1.8V. There's a thread on xtreme about dead processors, some had mad voltages running through them and were doing fine.
XMP profiles seem to be the same as profiles were before. I'm a bit unsure on this one, but then I set timings manually so haven't really looked into it. Reminds me that auto voltage is not a good idea on the processor, think I forgot to say that earlier.
That's my best shot. Pretty certain on all of the above, but think I've missed parts of your post. I'd like to know how you're cooling this system, if it's air I recommend buying cheaper ram or a cheaper processor and putting it on water. Board as well
Think you're going to have fun
