Overclock.net › Forums › Intel › Intel CPUs › CPU Load-Line Calibration -- LLC
New Posts  All Forums:Forum Nav:

CPU Load-Line Calibration -- LLC - Page 2

post #11 of 13
In case anyone is curious this is what it looks like without load-line calibration:

d1D46.jpg

and with load-line calibration: (CORRECTED)

transient_no_vdroop.jpg

The Intel default spec tries to prevent the voltage from ever spiking above the voltage set in BIOS to prevent the chip from frying itself in a changing load scenario. The voltage spikes when changing the load are called transient responses and is inherent to electronic circuits by design.
Edited by Doomtomb - 7/9/13 at 10:38pm
post #12 of 13
Quote:
Originally Posted by Doomtomb View Post

In case anyone is curious this is what it looks like without load-line calibration:

d1D46.jpg

and with load-line calibration:

DFMKR.jpg

The Intel default spec tries to prevent the voltage from ever spiking above the voltage set in BIOS to prevent the chip from frying itself in a changing load scenario. The voltage spikes when changing the load are called transient responses and is inherent to electronic circuits by design.
I'm not understanding something.
In my knowledge on full load, the voltage should be higher than idle.

But here I see the voltage under full load is lower, then it has a peek to reach idle.

Im I missing something??????

anyway a LLC of 100% would mean that the highest point of the peek doesn't exceed the maximum voltage?
And a LLC of 50% means the peek exceeds (or might exceed) the maximum voltage by it's halft?

For example in the 2nd graph a LLC of 50% would reach 1,26 volts? And a LLC of 100% reach 1,25 and LLC of 0% reach 1,27?
Or is it the opposite?


I see we need a file with all the terms explained...
post #13 of 13
Quote:
Originally Posted by qiplayer View Post

I'm not understanding something.
In my knowledge on full load, the voltage should be higher than idle.

But here I see the voltage under full load is lower, then it has a peek to reach idle.

Im I missing something??????

anyway a LLC of 100% would mean that the highest point of the peek doesn't exceed the maximum voltage?
And a LLC of 50% means the peek exceeds (or might exceed) the maximum voltage by it's halft?

For example in the 2nd graph a LLC of 50% would reach 1,26 volts? And a LLC of 100% reach 1,25 and LLC of 0% reach 1,27?
Or is it the opposite?


I see we need a file with all the terms explained...

You bring up some interesting questions, I will point to Anandtech for a more thorough explanation.
Quote:
Originally Posted by Anandtech 
During periods of high CPU demand, the VRM circuit works hard to supply the current required by the processor. However, as soon as that load is gone, the VRM circuit must act quickly in order to reduce the current supply to the level needed to match the new demand. Because it's impossible for the VRM circuit to respond instantaneously, the larger the load change the greater the maximum potential peak overshoot voltage. Controlling the magnitude of these peak values is critical for maintaining system stability. By positioning the processor's no-load (idle) voltage level higher during periods of light loading, it's possible to sustain a larger negative voltage dip without crossing the processor's lower specified voltage limit. In addition, "drooping" the load voltage as a function of supply current allows the VRM to effectively limit the maximum positive peak overshoot voltage (experienced during a heavy to light load transient) to a value below the maximum allowable CPU voltage. This resulting control system ensures the processor supply voltage, regardless of CPU load, never violates a specified limit.

Effectively, Vdroop (disabling load-line calibration and following Intel spec) is safeguarding the CPU against sudden unsafe voltage spikes. The Vdroop is the difference observed between the idle and full-load CPU voltage. The Vcore set in BIOS is the maximum voltage applied to the CPU during these changing load conditions if Intel spec is followed. If LLC is enabled, then the absolute maximum CPU voltage will be higher than Vcore. Voffset is the difference in voltage between the Vcore in BIOS and the idle CPU voltage. That is to say, if Voffset is 0 mV, then Vcore = idle voltage. If LLC is set to maximum, then full-load CPU voltage = idle CPU voltage but you will still get random spikes under changing load conditions.

This is a summary of the content of this page of the article with illustrations.

Not all this is necessary to understand, but it is concluded that Vdroop and Voffset are good things in maintaining system stability and prolonging the life of your motherboard and CPU. Really, with Haswell, the VRM circuitry for the CPU has been moved onto the chip off of the motherboard so these options will actually be disappearing in newer board revisions.

My best advice for overclocking is to find your max clock on stock voltage, then try increasing Vcore if you want to keep going. If your system just still isn't stable at your target overclock when putting the system under a stress test like Prime95, then try enabling Load Line Calibration.


I realized I made a mistake. My second image references Voffset being eliminated while still maintaining Vdroop.

This is what it looks like with no Vdroop:

transient_no_vdroop.jpg
Edited by Doomtomb - 7/9/13 at 10:37pm
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Intel CPUs
Overclock.net › Forums › Intel › Intel CPUs › CPU Load-Line Calibration -- LLC