Voltage Modding Innovations
Before telling you about the troubles we had as we tried to overclock LGA1150 processors, we want to remind you why voltage modification is so important. There is a correlation between a CPU’s clock rate and voltage. Both are at their minimum at low CPU loads. Then, as the CPU load grows up, the clock rate is increased to ensure higher performance and the voltage goes up to ensure stability. When the clock rate reaches its maximum thanks to the Intel Turbo Boost technology, the voltage reaches its maximum, too.
On ASUS mainboards, the standard correlation between clock rate and voltage is ensured by the CPU Core Voltage option, which is set at Auto by default.
While overclocking a CPU, we can increase its frequency multipliers above the default values. It means the CPU will work at higher clock rates, so we also need to increase its voltage to ensure stability. The simplest way to do this is increase the voltage to a certain value that would make the CPU stable at the maximum clock rate.
In this case, however, the voltage is going to be constant. It won’t drop at low loads when the CPU clock rate is lowered. It will remain high, even though the CPU doesn’t really need that. That’s why we try to avoid overclocking CPUs in this way. In the example below, you can see the voltage manually set at 1.150 volts.
Until now, we always tried to overclock CPUs by increasing their voltage in the offset mode. In this case, we only add or subtract an offset value from the default CPU voltage. The overall correlation remains the same: the voltage gets lower at low loads and higher at high loads. All power-saving technologies remain active in this case.
To change the voltage in this way, you have to set the CPU Core Voltage parameter at Offset Mode and specify whether the offset value is added or subtracted. In the example below the CPU voltage is increased by 0.145 volts:
Haswell-core CPUs support a third way of voltage modification. This adaptive method is preferable to the other two in that the frequency/voltage correlation doesn’t change at all in the standard frequency range. It is only when you increase the frequency multiplier above its standard values that the voltage begins to grow up along with the clock rate. And that’s exactly what we want to get while overclocking.
The adaptive mode combines the benefits of the other two, so the offset mode is hardly useful anymore. When you set the CPU Core Voltage option at Adaptive Mode, the CPU Core Voltage Offset option remains available but there appears the Additional Turbo Mode CPU Core Voltage option and an informational line that shows the sum of your voltage modifications. In the example below, we add 0.145 volts in the Offset mode (although you don’t have to do that unless necessary). We also add 0.015 volts to ensure stability at the maximum frequency, so the resulting CPU voltage will be increased by 0.160 volts.
That’s not all, though. Besides the new voltage modification method, the Haswell features an integrated voltage regulator. The mainboard now only supplies memory voltage and the so-called VCCIN voltage of 1.8 volts. The integrated regulator transforms this input voltage into all the different voltages required by the CPU’s subunits. And it does that with utmost precision – one or two thousandths of a volt. Voltage monitoring could only be checked out indirectly on mainboards, by power consumption or temperature. Some models even had check points for measuring voltages manually with a voltmeter because the mainboard’s own monitoring tools were often inaccurate. But now we can be absolutely sure which exactly voltage is supplied to the CPU cores. The voltage drop on the CPU at high loads isn’t a problem anymore, either. So, besides the voltage check points, BIOS options like Load-Line Calibration have become obsolete.
These new voltage modification capabilities would make LGA1150 processors perfect for overclockers if it were not for two downsides. First of all, the size of a Haswell CPU hasn't changed much compared to the size of an Ivy Bridge, which is manufactured on the same 22nm tech process. So, the small heat transfer area and the imperfect thermal interface between the CPU’s die and heat-spreading cap still hinder good overclocking.
Well, we would be quite satisfied with the same overclocking potential as offered by the Ivy Bridge series if it were not for the second and more serious problem. When the overclocked CPU is under high load, the praised integrated regulator goes crazy and lifts the CPU voltage suddenly. The extremely high voltage leads to a high temperature and we can't do anything about that. That's why the Haswell is worse than its predecessor when it comes to overclocking.
The developer says that the high voltage is necessary to ensure stability, but we don’t like this explanation. The voltage/frequency correlation is normal at the default settings even though we need the computer to be stable then, too. But as soon as the CPU frequency multiplier is increased even by x1, the integrated regulator steps the voltage up hysterically. It looks like an obviously error to us, but the CPU developer doesn't seem eager to correct it.