Testbed and Methods
We performed all our tests on a testbed built out of the following components:
- Mainboard: Gigabyte GA-Z87X-OC rev. 1.0 (LGA1150, Intel Z87, BIOS version F6)
- CPU: Intel Core i5-4670K CPU (3.6-3.8 GHz, 4 cores, Haswell, 22nm, 84 W, LGA1150)
- DDR3 SDRAM: 4x8GB G.SKILL TridentX F3-2133C9Q-32GTX (2133 MHz, 9-11-11-31-2N, 1.6 volts)
- Graphics card: Gigabyte GV-R797OC-3GD (AMD Radeon HD 7970, Tahiti, 28 nm, 1000/5500 MHz, 3072 MB of GDDR5 memory with 384-bit bus)
- Disk subsystem: Crucial m4 SSD (CT256M4SSD2, 256 GB, SATA 6 Gbit/s)
- CPU cooler: Scythe Mugen 3 Revision B (SCMG-3100)
- Thermal interface: ARCTIC MX-2
- PSU: Enhance EPS-1280GA 800 W
- Computer case: Antec Skeleton
We used Microsoft Windows 8.1 Enterprise 64-bit (Microsoft Windows version 6.3 build 9600), Intel Chipset Device Software version 188.8.131.527, and the AMD Catalyst 13.9 graphics card driver.
Operational and Overclocking Specifics
We had no problems assembling our testbed around the Gigabyte GA-Z87X-OC mainboard. It started up successfully, showing us the familiar picture with information about active hotkeys. You can enter the BIOS interface by pressing the Del key. The F9 key will open up a system info window, the same as you get when you press the same key in the BIOS. F12 shows a list of devices you can boot from. The End key launches the integrated BIOS update tool Q-Flash.
You can turn off the startup picture in the BIOS but there is no point in doing this. The mainboard will only show you the AMI logo but won’t tell anything about the startup procedure. It is hardly a downside because today's mainboards start up very fast and you can’t read anything from the screen anyway. To make the process even faster, you can enable Fast Boot in the BIOS.
As opposed to many LGA1150 mainboards, Gigabyte ones set standard settings when you choose Load Optimized Defaults in their BIOS. However, you can lower the idle power consumption considerably if you enable all of the power-saving technologies available in the BIOS.
To overclock the CPU or the whole computer automatically, you can use the recently implemented CPU Upgrade and Performance Upgrade features but, like any other automatic overclocking technology, they are imperfect. Moreover, they only work when you’ve got all of the BIOS settings at their defaults - this is mentioned in the user manual. The same requirement applies to the automatic overclocking via the OC Turbo button, making it far less convenient.
We like the OC Tag button, though. It can be pressed to load a user-defined set of parameters. You may want to use it to get back to the default settings or to load some basic failsafe overclocking profile from which to move further. We had to press the Direct to BIOS button often, too. Like the GO2BIOS button on MSI mainboards, it lets you enter the BIOS interface when starting up or rebooting rather than after first shutting the computer down completely (as is required for the DirectKey feature from ASUS). The single inconvenience is that when you prefer the classic BIOS interface, the Direct to BIOS button will get you into the insignificant System section where you can only adjust such parameters as date, time and interface language. It would be handier to find yourself right in the M.I.T. section where the bulk of overclocking options are.
The mainboard carrying a lot of buttons and switches, it may help to have the user manual open so that you could look up their purpose. Even despite the lack of free space, there is a shortened name next to each button, switch and other element written on the PCB, giving you a hint of what they do.
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 our 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.
Overclocking without changing any voltages is optimal for any CPU, and it is easy to do so on Gigabyte LGA1150 mainboards. You just switch the CPU Vcore and CPU Vcore Offset options in their BIOS from Auto to Normal. After that, the mainboard will keep its voltages at the default level rather than increase them automatically. And thanks to Intel’s power-saving technologies, the voltages will be lowered in idle mode.
Energy-efficient overclocking is even easier to do on MSI mainboards. If you leave the CPU voltage at Auto, it won’t be increased by the mainboard automatically after you adjust the CPU frequency multiplier. There are some nuances with MSI mainboards, though. The CPU frequency multiplier has to be changed in a special BIOS subsection, for example. On the other hand, when you set the above-mentioned options at Normal in Gigabyte’s BIOS, you can be sure that the voltages will stay that way. “Auto” is just too ambiguous.
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, when we test mainboards, we want to check them out under different conditions and loads, so we choose what overclocking method ensures the highest results. Higher clock rates and voltages mean harsher test conditions and it is under such conditions that we can better see any flaws or problems in mainboard design.
We used to increase voltage in the offset mode and the LGA1150 CPUs also support a similar adaptive mode, but such methods do not work well with Haswell-based CPUs. The fact is as soon as the default voltage is changed even by a tiny value, the Haswell’s integrated regulator will spot it and increase the voltage further at high loads, which means high heat dissipation, high temperature and, eventually, overheat. To avoid this, the Haswell must be overclocked at a constant voltage. The downside is that the CPU’s power-saving technologies cease to work: the CPU frequency multiplier drops at low loads but the voltage doesn’t drop anymore and always remains at the constant and high level. This is the only way to deal with the integrated voltage regulator, though. Moreover, it doesn’t affect the computer’s power draw in idle mode. That’s why we overclock our CPU to 4.5 GHz in our mainboard reviews, fixing the voltage at 1.150 volts and using the XMP settings for our memory modules.
When we overclock by fixing the CPU voltage at a certain level, some of the power-saving technologies get disabled. The CPU's frequency multiplier is lowered at low loads but its voltage always remains high. Anyway, we stick to this overclocking for the duration of our tests, especially as it doesn't affect the computer's idle power draw much.
By the way, earlier we published an article called Haswell and LGA 1150 Platform: Right Operation and Overclocking where we explained the basic rules for optimizing LGA1150 platform parameters and for overclocking Haswell-based CPUs on mainboards from different brands. There you will find our illustrated recommendations on enabling Intel’s power-saving technologies and increasing CPU power targets as well as on how to overclock Haswell-based CPUs with and without voltage adjustment.