Hi guys. I have been tossing an idea around in my head which I finally decided to try. I have a couple set OCs in my BIOS. One is a straight 4ghz at 1.32 Vcore (LLC on) and the other is 175 bclock Turbo OC (3.68->4.2ghz) at 1.31 Vcore (LLC on). The 4ghz has slightly higher Vtt tho, 1.21 vs 1.24 iirc.
Anyway, about LLC. I noticed previously that the amount of voltage drop was different depending on the turbo level (ie: how many cores are active). At 4 cores it was greatest, while 1 core had the highest voltage. When I went from my turbo OC to the 4ghz one, without even touching voltages I got 200x19 (3.8ghz) stable.
So, here's the theory: with vdroop, the CPU gets just the voltage it needs for a given speed. Since 4 cores are running slower in the turbo boost OC, they need less voltage than a single core running at much greater speeds. I wanted to test this out.
I disabled LLC with the 175 base clock turbo OC. It was not stable initially (1.31 nominal V dropped to 1.22 or so). I upped the voltage somewhat arbitrarily to 1.38V, which gave about 1.29V under load with 4 cores up to 1.36V on single core and idle at 1.38V. This was stable! I then increased the base clock a tad. I now have it running completely stable at 178 base clock for 3.75ghz up to 4.3ghz turbo! The voltage is only 1.30V under 4 core load, nominal is 1.39V. Here's the really nice thing tho: load temps are LOWER! I dropped about 4C doing this (compared both LLC on and off OCes consecutively so ambient was the same).
Verdict: If running a turbo boost OC, turn off LLC. On a straight OC (like my 4ghz OC) that doesn't use turbo boost, just run with LLC on because overall the voltage will be lower.
Still questioning: Intel's max voltage spec is 1.4V. With LLC on, you can get a steady 1.4V, but with LLC off, if you set it to 1.4V under load it's only 1.31 or 1.32V (4 cores). I would assume the 1.4V limit is under load conditions, but then VDroop is a part of their specifications... so is 1.4 nominal their limit?? Does anyone know?
For now, I'm very happy with this OC: 178bclk, turbo on. 1.38625V Vcore, 1.23V VTT.
Getting the RAM stable at 1424mhz CL7 was a bit of a pain. My RAM is rated 1600mhz CL8, I figured it could handle up to at least 1450mhz CL7 at 1.65V. So, 178 just wasn't stable even up to 1.40625V Vcore, 1.25V VTT... I decided to try a little more RAM voltage and voila! Stable. Dropped the vcore and vtt back down, RAM is at 1.675 or maybe 1.66875V. The great part is, I know for an absolute fact that my RAM is running as fast as it can at CL7 lol.