Voltage Regulation

Our voltage regulation testing is compromised of two factors being tested. Since this ASUS motherboard provides 'Loadline Calibration', we will be testing the vCORE fluctuation with and without this feature enabled in the BIOS on our stable overclock. Intel specification outlines a droop in voltage for Intel processors when switching from idle to load conditions. This droop is referred to as Vdroop in the overclocking community and generally regarded as a bad thing because it requires setting a higher vCORE to make up for the droop that occurs at load. Loadline Calibration in the ASUS BIOS is basically an option to eliminate the Vdroop from occurring. So our testing will not only be showing the difference between the two different states of Loadline Calibration, but it will also let us know how well Loadline Calibration does at eliminating Vdroop.

The second prong of our voltage testing will be a look at the various voltages and the differences encountered between what is selected in the BIOS, what the BIOS reports, what Windows reports, and what a calibrated digital multi-meter (DMM) find. We have only found three voltage read points on the motherboard so the vCORE, vDIMM, and vNB will be the only three recorded with the DMM. Both vCORE and vNB will be read from the underside of the motherboard at the output side of the corresponding inductor for each voltage supply. These read points have been the general consensus amongst enthusiasts as the universally correct read points on ASUS motherboards for a while now. vDIMM will be read directly from an open DIMM slot using the VDD pin closest to the key. The ground point used for all readings will be the ground pin on a fan header located at the bottom rear of the motherboard. Here are a trio of photos showing the various read points used.

Since we just looked at the read points, we'll start with a look at the voltages selected and reported. In the chart below, vCORE (LLC) is the vCORE with Loadline Calibration enabled and vCORE will be with Loadline Calibration disabled. Here is how things shake out:

As we can see, the BIOS selections are very close to what is presented in the BIOS as readings for pretty much all of the voltages. This is a welcome sight as it isn't always fun trying to remember what voltage offsets are all the time. The readings in Windows via PC Probe II carry over the accuracy which is fully expected as the voltages are likely polled from the same place as the BIOS does, the one exception being the vDIMM reading by PC Probe II. It appears to be the same reading as the BIOS, but our DMM found a slightly lower result with 0.05v less than the software readings. This equates to exactly what we set in the BIOS. The vCORE, and vNB DMM readings are almost bang on as well to the software which means these software readings should be trusted. It is hard to say whether this is the case across a number of the samples of this motherboard, but hopefully that is the case with others. Let's now have a look at a couple of OCCT vCORE charts over a two hour stress test.

Keep in mind that this result is with our highest stable overall overclock at 4.1GHz w/1.36875 set in the BIOS so as to stay above 1.30v under load. The Vdroop visible with the dual core E8400 is exactly what we should expect going from 1.33v down to 1.30v for a total droop of 0.03v. The two spikes we see in the voltage reading are a bit disconcerting and subsequent repeats of the test failed to show these spikes again. In all likely-hood, it was simply a miss-read from the software.

Once we enable Loadline Calibration, we can immediately drop the vCORE selected in the BIOS to 1.3125v for stability at this overclock. The vCORE right across is straight as an arrow showing absolutely zero ripple according to OCCT. As random checks with the DMM throughout the test, it was found to be within a hundredth of the same value every time. The voltage under load required to maintain stability isn't any less, or more, but the voltage then being fed to the CPU at idle is less than if we have Loadline Calibration disabled. This is what enthusiasts don't like about Vdroop, it requires a higher vCORE to be used when at idle than if there was no droop. Some boards are really bad with droop, the Rampage Formula isn't one of those, even with Loadline Calibration disabled. Keep in mind though, we have only looked at a dual core CPU, not a quad core which will likely increase the amount of droop slightly.