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Haswell Overclocking

Have you set up your Haswell-based computer as described in the previous section? Well, now it’s time to overclock it if you’ve got a special K-indexed model with unlocked frequency multiplier and your mainboard is based on the Intel Z87 chipset. Ordinary LGA1150 CPUs and other chipsets are not designed for overclocking. We want to warn you against using any automatic overclocking technologies for the CPU or the platform at large. Although easy to use, they are not efficient. Different mainboard makers have different overclocking algorithms, yet we can see no good ones among them. There are some satisfactory algorithms but the rest of them are just bad. It is always better to select optimal parameters manually for the specific CPU, considering its power and cooling systems.

On the other hand, it is quite acceptable to achieve a small but instantaneous performance boost by changing Intel Turbo Boost parameters via BIOS options like Multi Core Enhancement or Enhanced Turbo. In this case, the CPU can increase its frequency multiplier at high loads to the maximum level which is normally used by Turbo Boost for single-threaded loads only. For example, with an Intel Core i5-4670K, the clock rate will be 3.8 GHz at any load instead of changing dynamically from 3.6 to 3.8 GHz.

Gigabyte mainboards offer a more productive version of the enhanced Turbo mode, which is enabled via the “K OC” option. It increases the CPU frequency multiplier by x2 not only at peak load but at other loads as well. As a result, the CPU will be clocked at 3.8 GHz at high loads, at 3.9 (instead of 3.7) GHz when three of its cores are in use, and at 4.0 GHz when only one or two CPU cores are in use.

Energy efficient overclocking is only possible if you don’t increase voltage. It will ensure higher performance and, despite the increased power consumption, you can expect long-term savings due to the reduced amount of energy spent for each computation. Energy efficient overclocking is going to be environment-friendly as we showed in our Power Consumption of Overclocked CPUs review. However, you cannot overclock by simply setting a higher multiplier for the CPU clock rate. In this case, the mainboard will automatically increase CPU voltage, aiding inexperienced overclockers who, trying to quickly reach maximum results, tend to forget that higher voltage is needed to ensure stability at high clock rates. Older mainboards wouldn’t start up or boot the OS up in that case but now the smart BIOS will increase the voltage so that the computer could boot up. The CPU may even pass stability tests with such settings.

Like any automatic overclocking, this method is far from efficient. It is especially inappropriate for the Haswell generation. Sensing that the mainboard has increased the input voltage, the CPU’s integrated regulator will increase it even further at high loads, most likely provoking overheat. That’s why we need to “tell” the mainboard that its aid is not called for when we overclock without increasing voltage.

It is easy to do on Gigabyte mainboards. You just switch the CPU Vcore and CPU Vcore Offset options in their BIOS from Auto to Normal. After that, the mainboard will stop to increase voltage automatically. Working in the classic BIOS interface, you will find these options on the CPU Core Voltage Control page, which is located in the Advanced Voltage Settings subsection of the M.I.T. section.

If you prefer the new Gigabyte UEFI DualBIOS interface, these options will be available on the very first page you can see when you enter the BIOS. By default, it provides a lot of various options to quickly adjust clock rates, frequency multipliers and voltages. You can edit the contents of that page and remove some of its options. In that case, you will find the abovementioned features by choosing Performance -> Voltage -> CPU Core Voltage Control.

The rules for energy-efficient overclocking (without any voltage increase) are not as simple for mainboards from other brands as for Gigabyte. If you increase your CPU clock rate on an ASUS mainboard but leave the CPU Core Voltage option (in the Ai Tweaker section) at Auto, the voltage will be increased automatically. To avoid that, you have to switch CPU Core Voltage at Manual and leave the rest of the options intact. In this case, the mainboard won’t step the voltage up and the latter won’t be increased further by the Haswell’s integrated regulator.

It may be confusing which BIOS options can be left at Auto and which not. Mainboards from Intel and MSI are simpler in this respect but have problems of their own. The DZ87KLT-75K is the only Z87-based product from Intel, so it is the only one to be able to overclock LGA1150 CPUs. If you want to change the CPU frequency multiplier, you can do this in the Cores block of the Performance section by entering numbers or moving the slider. You don’t have to do anything about voltages.

But besides setting a required CPU frequency multiplier, you need to manually increase the power limits (in the previous section we explained how to find them in the BIOS). Otherwise, the multiplier will be dropped at high loads. In fact, you had to do so on every mainboard in the past, but then all of them learned to automatically set up the power limits depending on user-defined parameters. The Intel DZ87KLT-75K can correct the power limits, too, but only during automatic overclocking. If you overclock manually, you have to correct them manually as well. That's not hard, but somewhat inconvenient.

Energy-efficient overclocking is possible on MSI mainboards, too. If you leave the CPU voltage at Auto, it won’t be increased by the mainboard and by the CPU’s integrated regulator automatically. There’s one important nuance, though. All fine-tuning and overclocking options are collected in one huge “OC” section of MSI’s BIOS. At the very top of it, there is an option called “Adjust CPU Ratio” which is likely to be used by most people in the first place to adjust the CPU frequency multiplier.

And that would be bad because the mainboard disables Enhanced Intel SpeedStep as soon as you Adjust CPU Ratio in any way. The EIST option becomes not just disabled but even unavailable, so you cannot turn it back on manually. To avoid this, you should change your CPU frequency multiplier in the CPU Features subsection of MSI’s BIOS - it is at the bottom of the OC section. There is a separate multiplier for each of the CPU cores, so you have to enter the same number for each of them.

Energy-efficient overclocking can be done on ASRock mainboards but in the most inconvenient way. You cannot just increase your CPU frequency multiplier as it will make the voltage too high automatically. As opposed to mainboards from other brands, you must explicitly specify the default voltage on the CPU cores. The problem is that the standard voltage varies between CPU samples, so the exact value has to be found by trial and error, basing on the monitoring data available in the BIOS.

That’s not all, actually. As soon as you change your CPU frequency multiplier on an ASRock mainboard, the CPU input voltage will be increased from 1.8 to 1.9 volts. Besides that, the option of compensating for the CPU voltage drop will be set to its maximum while the fans will be accelerated to their top speed. Fortunately, as opposed to MSI mainboards, you can manually roll these settings back to their previous values. For the fans, you just have to choose Customize instead of the standard speed regulation mode. Still, ASRock’s LGA1150 mainboards are not as good as their predecessors in terms of overclocking convenience.

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