If this is the first time changing BIOS settings, relax. Just follow my instructions. Once your machine starts to boot, click “DEL.” Your computer should enter the BIOS main page. In the main page, you can see many settings. All the overclocking settings are located in the MB Intelligent Tweaker (M.I.T.). Before we go there, first click on “PC Health Status”. Like the picture on the right, you should be able to see the voltages of the processor, DDR3, and temperatures of the processor and North Bridge. This page helps you to watch the current system status. Next go to M.I.T. and we will begin our quest for 4GHz. With the Core i7 platform, the CPU clock is calculated by multiplier times Bclk. For example, the i7 920 is rated 2.66GHz, (20X133MHz = 2660MHz). 133MHz is the Bclk, 20 is the multiplier. For the i7 920, the multiplier is locked by Intel, so there is only one way to raise the frequency of the i7 920, and that is to raise the Bclk!. So for our goal of 4GHz, Bclk must be 200MHz. with i7 architecture, when you change Bclk, you also automatically change the other components frequency such as QPI Speed, Memory Speed and Uncore frequency.

To avoid causing system instability or a failed overclock, I use a process of elimination to make sure the frequencies set will work with my hardware. When Bclk is 200MHz (auto setting), the memory will go over 2000MHz. In this case I am using Corsair DDR3- 1333, so I don’t know if my memory will work at 2GHz. Not wanting to waste time, I drop the frequency of the memory to 1333MHz or lower. After I ensure the CPU at 4GHz is stable, I can then raise the memory with specific ratios to see if the memory can go higher. Same for QPI and Uncore. By this process of elimination, we try to keep the components at default to see first if that can reach our 4GHz target.

When raising Bclk to 200MHz, if other components keep the same ratio, Uncore, QPI and DDR3 will go up as well. As diagram C shows, Uncore and DDR3 are near to default level. If the 4GHz overclock fails, you know it is either the Bclk or QPI settings causing it to fail.

Now, follow my settings. First, in Advanced CPU features, I disabled some functions related to power savings and Turbo Boost. Enabling these features causes the CPU frequency to be adjusted according to loading. This will cause confusion about real-time frequency, so disable them first. Then go the M.I.T. and change the QPI Link Speed to x36. With Bclk at 200MHz, QPI speed will 7.2GT/s, which is much higher than the default of 4.8GT/s. Don’t worry, later we will add some voltage to QPI to make it stable.

Next, set Bclk frequency to 200MHz. The GIGABYTE BIOS calculator will automatically calculate the other components frequency, and you can see the settings in blue. CPU clock is 4.00GHz, yes that’s our goal. QPI link speed is 7.2GT/s, memory frequency is 1600MHz. Using Corsair DDR3-1333MHz, if running with 1600MHz, I am not sure if it will be stable or cause system fail, and memory needs more time to test for stability, so I drop the memory ratio to 6x, forcing the memory to run DDR3-1200MHz. Yes, this is lower than rated, so I am sure with this memory frequency that won’t be the reason to cause my 4GHz overclock to fail.

For Uncore Frequency, the BIOS allows users to change the ratio to what they want, but the i7 processor still has some limits, because it still needs to follow some logic formula from Core i7. The formula is, Uncore speed needs to be 2x speed of memory or ratio of 2x+1. In theory, the higher the Uncore speed, the better the performance because it gives memory and other components inside the processor a boost and more bandwidth. I use the same way to avoid Uncore settings causing instability, so the safe way is to force the Uncore to run at 2.4GHz (2x of DDR3 speed). But, I soon figure out that the i7 can’t accept this ratio due to a logic bug, so I raise the ratio to 2x+1. Uncore is now running at 2.6GHz. The same for memory, so I now know that Uncore will not cause the 4GHz overclock to fail. So recapping, I set Bclk to 200MHz, CPU is 4GHz, Uncore 2.6GHz and DDR3 at 1200MHz. Uncore and DDR3 is lower than default rated speed, so I know we are giving them enough voltage to operate.

We just set up all our frequencies, so the next step is to change voltage. Bclk is 200MHz, and CPU 4GHz, so only CPU vcore voltage is affected. For this parameter set it to 1.4000v or higher. QPI speed will be affected by QPI/VTT and QPI PLL voltages. Usually QPI/VTT will affect more. Set QPI/VTT to 1.515v, and leave QPI PLL to auto or default. For the other voltages, keep at auto. Then click F10 to save settings and leave BIOS. After rebooting, the screen shows our overclock was sucessful. Our Core i7 920 now is 20x200MHz, or 4GHz.

When the processor is under stress and full loading, the processor is only at 53°C temperature. This is quite low. The temperature of the North Bridge is only 33°C as well. This is a good sign that our CPU can go higher than 4GHz. So, in Easy Tune 6, I pulled the CPU vcore to 1.5v , and in BIOS turned on Turbo Boost. The multiplier climbed to 21x, and CPU frequency becomes4.2GHz. After running 3DMARK VANTAGE , our CPU score is 24772.

After successfully overclocking our i7 920 to 4GHz, I did some fine tuning to overclock the memory. First, I used the process of elimination to make sure 4GHz was stable at the lower DDR3 and Uncore frequencies. After stress testing, we found it was stable. So next I am going to try to overclock the memory and Uncore frequencies. Like in picture C, raising the memory divider ratio to 8x, DDR3 will overclock to DDR3-1600MHz. Remember, raising the memory means we need to raise the Uncore frequency as well. In this case, I set the Uncore frequency to 3.4GHz and kept the same DDR3 voltage at 1.5V. Then I tested using Memtest. As the picture on the right side shows, Memtest was able to complete with no errors, meaning, our overclocking settings were successful.