Why do mb's have the llc option then?
Leaving it alone is also not the right answer because in some cases the motherboard will default to the most aggressive level of LLC and the overshoots are ridiculous on the high-side. (as was the case with my MIVE-Z)
One may not like the notion or concept of LLC, but one cannot simply ignore it either. Not without elevating the risk to their CPU.
Yeah, figure 3 is pretty amazing. That you have these detectors all over the place and you can get massively different readings depending on where you are... I mean, it makes intuitive sense, but seeing it - and seeing the magnitude of the delta - is something else. Previously I had this idea that a grid is a grid and pretty much all the points to pull power from move more or less together and droop was createdout on the external regulator. I don't think that I'd really internalized how much of a delta you could get on chip in a specific region (unless you messed up the grid by forgetting to contact it or something) but then you see how much of a delta there is across the die and you can see how large a delta you can get within a die over a short period of time.
I meant to comment on the magnitude of the delta as well. It was easily a whole order of magnitude higher than the absolute worst-case I had assumed it would be.
I was expecting something on the order of hundreds of microvolts of droop, not something on the order of tens of millivolts
No wonder Intel specs the Vcc to be so large, seemingly, when they bin their chips in comparison to how much undervolting we enthusiasts find ourselves comfortable with when we run a rather unqualified "stress test" and declare our 0.8V 4GHz 3770K to be "stable" :whiste:
There is a solid 0.1V of margin Intel needs to build into their Vcc spec just to ensure they've got the intra-die Vdroop covered. Simply fascinating.
I also couldn't help but wonder just how much of this "droop net" technology has made its way into Haswell, complete with the necessary analog logic being added to the existing power regulation circuitry in the established PCU, to couple synergistically with the on-package VRMs to minimize power-consumption by reducing the necessity of maintaining such a large Vcc margin as needed to counter-act the intra-die droop... I see opportunity to do very elegant and sophisticated stuff there.