ASUS P5Q PRO P45 Motherboard Review

by MAC     |     July 28, 2008

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 is reported by digital multi-meter (DMM). We have found five voltage read points on the motherboard so the vCORE, PLL, vFSB/VTT, vNB, and vDIMM will be 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. PLL and vFSB/VTT voltages will be read from points on the top of the motherboard. 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 a screw hole. Here are a few photos showing the various read points used.

Now that we have established where the read points are, letís have a look at the results. In the chart below, vCORE (LLC) is the vCORE with Loadline Calibration enabled and vCORE will be with Loadline Calibration disabled. These measurements were taken at 7x400Mhz, the highest officially supported FSB, and the FSB that will most likely be used by those seeking mild overclocks. Everything else in the BIOS is set to auto. Here are our extensive findings:

As you can seeÖwe have a lot to talk about, so letís examine each voltage separately.
  • vCore: Overall, even without the benefit of LLC, this board displays good vCore regulation with minimal vDroop. The BIOS selections are within 3% of the actual readings for pretty much all of the voltages, which is quite commendable. At the auto setting, the vCore is set a little high, but it will allow novice users achieve respectable overclocks without fiddling with the vCore settings.
  • vCore (LLC): The solid vCore regulation obviously gets even better once LLC is enable. In fact, vDroop is eliminated and thereís actually a bit of vBoost under load. Quite impressive.
  • PLL: As you can see, the first two settings are set very high when compared to Intelís recommended 1.50V Ī 5%. However, there is no conclusive evidence that PLL can cause long-term harm to a CPU, and we canít formulate our own opinion without long-term testing of PLL-related issues. Having said that, we recommend that users manually set this option to 1.54v just to be safe. Also, it is quite possible that the BIOS will lower this setting when a 45nm chip is detected.
  • vNB: Overall, we are very satisfied with the northbridge voltages, which display superior stability across the board. Once again there is a bit of overvolting at the auto setting, but it was likely implemented to ensure that all P5Q PROís would be able to achieve their FSB1600 specification without unnecessary user tinkering.
  • vDIMM: ASUS motherboards are well-known for overvolting the memory by between 0.06-0.10V, and we do not see any issues with this, as long as the user is aware that it is happening.
  • vFSB/VTT: From 1.24V onwards the VTT is perfectly acceptable. However, the auto and 1.20V settings are quite high. Recently, there have been countless debates about the effects of VTT on the long-term health of 45nm chips, and the general consensus is not to use over 1.40V on a 24/7 basis. However, once again, it is quite possible that the BIOS would lower the VTT to a more reasonable auto setting when it detects a 45nm chip.
Now letís recap a few important facts. Every individual motherboard is different, and it is entirely possible that our sample is alone in displaying any and all of the above voltage characteristics. Also, the motherboard did not significantly overvolt the PLL and FSB/VTT voltages when using a 266Mhz and 333Mhz FSB, they remained at 1.55V and 1.22V respectively on the auto setting.

Now letís have a look at a couple of OCCT vCORE charts over a two hour stress test.

vCORE w/Loadline Calibration Disabled

This result was with the processor set to 8x400Mhz with a 1.325 vCore. Overall, the regulation looks quite good. The slight vDroop is noticeable once the stress test actually kicks-in, but otherwise the fluctuations are quite minimal, and there are no zero worrisome spikes. Evidently, the eight-phase power design is doing it's job quite well.

vCORE w/Loadline Calibration Enaled

This time once the stress test kicks-in the motherboard actually increases the vCore by almost 0.01V, which should help ensure stability under heavy load. As you can see, once the test gets going the vCore is straight as an arrow until the last 5 minutes, when OCCT enters the low load monitoring stage.

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