- Feb 2, 2008
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If you've ever overclocked a system, chances are that at some point or another you've had opportunity to become upset with your Vdroop "problem." Some users, confused as to why their system refuses to exactly match actual processor supply voltage to the value specified in BIOS, are quick to blame the quality their motherboard; still others find fault with the difference noted between their board's idle and full-load processor supply voltages. Actually, load line droop (Vdroop) is an inherent part of any Intel power delivery design specification and serves an important role in maintaining system stability. In most cases, comments regarding unacceptable power delivery performance are completely unfounded. To make matters worse, unjustified negative consumer perception surrounding this often misunderstood design feature eventually forced a few motherboard manufacturers to respond to enthusiasts' demands for action by adding an option in their BIOS that effectively disables this important function.
Overclocking... The Rules Have Changed
How have the rules changed? vdroop certainly isn't a new thing for 45nm parts.
Doing this seems like a really bad idea to me. Vdroop is used to cut costs - basically, they can use less capacitance on the output of the voltage regulator and still supply "good enough" power to the CPU by simply overvolting it slightly when it's not drawing much current, and undervolting slightly when it's drawing a lot of current.
The naive reaction would be, "well, I'll disable this and always supply the right voltage". A user does that, and verifies with some voltage measuring tools (a multimeter, software, whatever) that the voltages look better. But the user missed what really changed. With active voltage positioning enabled, the transient spikes in the power supply are reduced but the steady-state voltages look worse. With it disabled, the steady-state voltages look better, but transient spikes will be worse (and AFAIK there is no way for software to detect the transients). If the CPU suddenly transitions from idle to load, there will be a brief moment when it is significantly undervolted (and, like any undervolted CPU, may crash / corrupt your data / whatever).
linear
thetechrepository
And yeah, don't mess with Vdroop. Doing the pencil mod or enabling Load Line Calibration and setting the voltage in BIOS lower, say from 1.412 to 1.345, isn't really going to help you much. Right when the load starts, the voltage will still dip to the same level as before, and then stabilize at just below the new now lower BIOS vcore of 1.345V, and when going from load to idle, it will shoot back up to your old BIOS vcore of 1.412V, possibly higher, and then stabilize at 1.345V again. This takes only milliseconds, not enough for any software to measure, but in those milliseconds your cpu can crash. So don't get rid of Vdroop. If you need higher load voltage, just increase vcore in BIOS. The vcore set in BIOS is just the maximum specified voltage, not the actually vcore you run anyways.
"Vdroop" exists because Intel decided that it's needed. There was at least this article here at anandtech that explained voltage dropping under load:
Everything I say in following assumes that the charts in this article are correct, and show exactly the idea of what happens.
So "Vdroop" is a GOOD thing, because it reduces the variance in processor vcore. It is also a bad thing for those that care more about their average vcore than their absolute maximum vcore value at some short moment. Personally I'd rather have less vcore variance and a bit higher average vcore than more variance and lower average.
I think it goes like this:
Too little voltage - and you experience errors in CPU work. That means instability. But I doubt it damages the hardware. (just software, in a way)
Too much voltage - and you shorter the lifespan of your CPU. I do not know the details. This can damage hardware. (who needs software after that?)
The optimal amount of vdroop is a mystery though. Too much vdroop and the variance is again greater than it would be without vdroop. Perhaps the ideal value depends on motherboard and processor used? Never trust your motherboard manufacturer though, and it wouldn't surprise me a bit that your mobo manufacturer (or maybe their BIOS team) just puts some value there, which ends up being not-so-ideal. Hopefully some other poster knows more abut this.
Forum people that say "motherboard A is better than B, because A has less vdroop" annoy me a bit... at least after reading this anandtech article. For overclockers who aren't ready to break their hardware, the following question is relevant: "Will running my CPU with a higher average vcore cause me more trouble (that can be a shorter CPU lifetime or lower achievable OC or marginally higher power usage) than running my CPU with a lower average vcore, but higher occasional vcore?" (that occurs when CPU load drops). Of course assuming that the Vdroop solution in question does what it is meant to do....
EDIT: Original Poster... do you have C1E and/or EIST enabled in BIOS?? Vdroop is about the voltage drop that occurs when your CPU is *under load*. The power saving mechanisms will probably both lower your CPU multiplier to 6 and also lower your vcore if your processor is at *idle state*!
Disable the power saving options to see if your vcore is the same than what you set it to be. After that run some CPU stressing application and during the run, open CPU-Z and check your vcore to see the "Vdroop".
So, are people going to continue doing pencil mods?