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We have already seen Asus EFI BIOS and discussed it in the previous Asus mainboard reviews. It proved to be a pretty successful implementation of the UEFI standard (Unified Extensible Firmware Interface). The new EFI BIOS from Asus looks unusual, but its internal structure and the variety of available settings remind us of the previous versions of Asus BIOS. We really liked it that by default we immediately see feature-rich “Advanced Mode” instead of a simpler “EZ Mode” operational environment.

The first section in the menu is called “Extreme Tweaker”, which contains most of the options related to overclocking and system fine-tuning.

I was a little disappointed that we couldn’t start the system with our AMD FX-8150 processor right away. First we had to update the BIOS version to 0813 using an old AM3 processor, since it was already available for download. Only mainboards with this BIOS version dated October 7, 2011 or newer support new AMD FX processors, which means that all mainboards manufactured before that date will be incompatible with the new CPUs, so keep it in mind.

The nominal operation mode with default settings also didn’t please us too much. By default the mainboard set the memory timings to extremely high values of 9-9-9-24-1T, all power-saving Cool’n’Quiet and C1E technologies were disabled. The nominal frequency of our AMD FX-8150 processor is 3.6 GHz, but even when all cores are utilized, the CPU can increase its clock rate up to 3.9 GHz, and under lower loads – up to 4.2 GHz. These were publicly known facts, but no one could explain why under heavy load the CPU frequency would drop down to 3.3 GHz not only during overclocking, but also in the nominal mode. During our experiments we discovered that enabling “HPC Mode” parameter in the “CPU Configuration” section prevents the frequency from dropping like that. Although, I have to admit that this parameter works in a very unique way. Even when it has been enabled, the processor frequency may still drop, so you will need to cut off all power to prevent this from happening. The opposite is also true. Once we have enabled the “HPC Mode”, we could successfully complete our tests in overclocked mode and there was no frequency drop of any kind. However, when we saved the BIOS settings profile, we suddenly noticed that this parameter got disabled, though the frequency didn’t drop.

AM3+ processors can be easily overclocked due to their unlocked clock frequency multiplier: all you need to do is to increase their multiplier and core voltage. It is very hard to confirm the system stability, because LinX utility refused to do this, so we had to resort to time-consuming tests in Prime95. It is even harder to ensure that the system runs in acceptable thermal conditions, because during overclocking its heat dissipation and power consumption increase dramatically. At first we were shooting for 4.6 GHz frequency, but we interrupted out tests when the thermal diode under the processor socket reported 86°C.

Unfortunately, we can’t use the CPU core temperature readings, because they are reported 15-25°C lower than the readings we take off the thermal diode under the CPU socket, and no one really knows how they differ from the real temperatures. The dependency is non-linear: as the operational load and temperatures increase, the difference reduces. Suppose it drops to 10 or even 5°C. 86 + 5 makes 91°, according to our most reserved estimates. Moreover, it is important to keep in mind that these numbers are taken on an open testbed with additional air-cooling in place. The temperature will obviously reach and even exceed 100° inside a closed system case, and conditions like that are totally unacceptable. Therefore, we had to give up or plan to hit 4.6 GHz mark with our particular processor and our specific cooling system.

We managed to confirm system stability when we overclocked our processor to 4.5 GHz, although it was still working in not the most favorable conditions. According to the diode, the CPU temp reached 80° during our Prime95 tests, the system power consumption increased to 440 W, the heatsinks on the processor voltage regulator components were scorching hot despite the additional fan we had installed right above them – they still heated up to over 60°C.

It may seem like there is not much you can do about it, this is just the way new AMD processors turned out to be, but later when we tested MSI 990FXA-GD80, we discovered that its power consumption in overclocked mode and similar testing conditions was significantly lower. We couldn’t perform a fair direct comparison, because the MSI board was unable to overclock our processor to 4.5 GHz frequency, but it made us go back to more overclocking experiments with our Asus Crosshair V Formula mainboard. One significant difference during overclocking was the fact that MSI mainboard didn’t have functionality that could counteract the processor core voltage drop under heavy load. As for Asus board, you could even set the intensity of this counteraction, which we did: we set the “CPU Load Line Calibration” parameter to “High”, which stood for 50%.

It turned out that enabling this feature does seriously increase the system power consumption. However, if we disable “CPU Load Line Calibration” completely, then we will have to increase the CPU Vcore even more to overclock our processor to the same frequency. With this technology enabled we only added 0.1625 V, while without it we had to increase the CPU Vcore by as much as 0.2375 V, so the end-results were, obviously, ambiguous. Take a look at the system power consumption when the processor is overclocked to 4.5 GHz and compare the results with the enabled and disabled “CPU Load Line Calibration” technology:

In order to ensure that under heavy load the processor has sufficient voltage coming in, we have to raise it above the level we have with the working “CPU Load Line Calibration”. As a result, it becomes excessive in idle mode and under low operational loads, which leads to much higher system power consumption in these modes. However, under heavy loads the power consumption turned out significantly lower, which had a positive effect not only on the electrical, but also on the thermal parameters. Now even during long tests in Prime95 the temperature only hits 72°C, according to the diode under the processor socket, the heatsinks temperature barely exceeded 50°C, and the total system power consumption went beyond 400 W only when we overclocked the system memory at the same time. The mainboard was capable to have the memory work stably at 1867 MHz.

We always overclock our system so that it could be used in this mode for a long time. At the same time we do not try to make our life easier by disabling some of the mainboard features, such as additional controllers, for example. We also do our best to make sure that all processor power-saving technologies stay up and running normally. So, in this case all power-saving technologies were working fine even during overclocking, so the processor Vcore and clock multiplier were dropping in idle mode as they are supposed to.

However, it would be incorrect to assume that the technology preventing the processor core voltage from dropping under heavy load is doing more harm than good and needs to be disabled during overclocking. Yes, disabling “CPU Load Line Calibration” did have a positive effect on system operation when our processor was overclocked to 4.5 GHz, however, we couldn’t overclock our CPU to 4.6 GHz without this technology. To ensure system stability at 4.6 GHz processor clock speed, we had to raise the processor Vcore so much that it started to work against us. Therefore, we decided to enable “CPU Load Line Calibration” technology back on, but this time switch to the “Medium” mode, which is equivalent to only 25%. However, a few minutes into the Prime95 test the increased to 420 W system power consumption forced us to terminate the testing. The barely noticeable 2% performance gain, which is exactly what the system gets from overclocking the processor by additional 100 MHz doesn’t justify the seriously aggravated power and thermal characteristics.

 
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